Allocation of radio resources for vehicular communication

ABSTRACT

The invention relates to an improved radio resource allocation performed by a vehicular mobile terminal. The vehicular mobile terminal determines whether to determine radio resources based on the location of the vehicular mobile terminal or not, based on information received from an entity of the communication system. In case the radio resources are to be selected based on the location of the vehicular mobile terminal, the vehicular mobile terminal determines the location of the vehicular mobile terminal, and determines radio resources for communication with at least the second mobile terminal, based on the determined location of the vehicular mobile terminal.

BACKGROUND Technical Field

The present disclosure relates to improved allocation of radio resourcesfor a vehicular mobile terminal. The present disclosure is providing thecorresponding vehicular mobile terminal, the radio base station, thesystem, and method.

Description of the Related Art Long Term Evolution (LTE)

Third-generation mobile systems (3G) based on WCDMA radio-accesstechnology are being deployed on a broad scale all around the world. Afirst step in enhancing or evolving this technology entails introducingHigh-Speed Downlink Packet Access (HSDPA) and an enhanced uplink, alsoreferred to as High Speed Uplink Packet Access (HSUPA), giving a radioaccess technology that is highly competitive.

In order to be prepared for further increasing user demands and to becompetitive against new radio access technologies, 3GPP introduced a newmobile communication system which is called Long Term Evolution (LTE).LTE is designed to meet the carrier needs for high speed data and mediatransport as well as high capacity voice support for the next decade.The ability to provide high bit rates is a key measure for LTE.

The work item (WI) specification on Long-Term Evolution (LTE) calledEvolved UMTS Terrestrial Radio Access (UTRA) and UMTS Terrestrial RadioAccess Network (UTRAN) is finalized as Release 8 (LTE Rel. 8). The LTEsystem represents efficient packet-based radio access and radio accessnetworks that provide full IP-based functionalities with low latency andlow cost. In LTE, scalable multiple transmission bandwidths arespecified such as 1.4, 3.0, 5.0, 10.0, 15.0, and 20.0 MHz, in order toachieve flexible system deployment using a given spectrum. In thedownlink, Orthogonal Frequency Division Multiplexing (OFDM)-based radioaccess was adopted because of its inherent immunity to multipathinterference (MPI) due to a low symbol rate, the use of a cyclic prefix(CP) and its affinity to different transmission bandwidth arrangements.Single-carrier frequency division multiple access (SC-FDMA)-based radioaccess was adopted in the uplink, since provisioning of wide areacoverage was prioritized over improvement in the peak data rateconsidering the restricted transmit power of the user equipment (UE).Many key packet radio access techniques are employed includingmultiple-input multiple-output (MIMO) channel transmission techniquesand a highly efficient control signaling structure is achieved in LTERel. 8/9.

LTE Architecture

The overall LTE architecture is shown in FIG. 1 . The E-UTRAN consistsof an eNodeB, providing the E-UTRA user plane (PDCP/RLC/MAC/PHY) andcontrol plane (RRC) protocol terminations towards the user equipment(UE). The eNodeB (eNB) hosts the Physical (PHY), Medium Access Control(MAC), Radio Link Control (RLC) and Packet Data Control Protocol (PDCP)layers that include the functionality of user-plane header compressionand encryption. It also offers Radio Resource Control (RRC)functionality corresponding to the control plane. It performs manyfunctions including radio resource management, admission control,scheduling, enforcement of negotiated uplink Quality of Service (QoS),cell information broadcast, ciphering/deciphering of user and controlplane data, and compression/decompression of downlink/uplink user planepacket headers. The eNodeBs are interconnected with each other by meansof the X2 interface.

The eNodeB s are also connected by means of the S1 interface to the EPC(Evolved Packet Core), more specifically to the MME (Mobility ManagementEntity) by means of the S1-MME and to the Serving Gateway (SGW) by meansof the S1-U. The S1 interface supports a many-to-many relation betweenMMEs/Serving Gateways and eNodeBs. The SGW routes and forwards user datapackets, while also acting as the mobility anchor for the user planeduring inter-eNodeB handovers and as the anchor for mobility between LTEand other 3GPP technologies (terminating S4 interface and relaying thetraffic between 2G/3G systems and PDN GW). For idle-state userequipments, the SGW terminates the downlink data path and triggerspaging when downlink data arrives for the user equipment. It manages andstores user equipment contexts, e.g., parameters of the IP bearerservice, or network internal routing information. It also performsreplication of the user traffic in case of lawful interception.

The MME is the key control-node for the LTE access-network. It isresponsible for idle-mode user equipment tracking and paging procedureincluding retransmissions. It is involved in the beareractivation/deactivation process and is also responsible for choosing theSGW for a user equipment at the initial attach and at the time ofintra-LTE handover involving Core Network (CN) node relocation. It isresponsible for authenticating the user (by interacting with the HSS).The Non-Access Stratum (NAS) signaling terminates at the MME, and it isalso responsible for the generation and allocation of temporaryidentities to user equipments. It checks the authorization of the userequipment to camp on the service provider’s Public Land Mobile Network(PLMN) and enforces user equipment roaming restrictions. The MME is thetermination point in the network for ciphering/integrity protection forNAS signaling and handles the security key management. Lawfulinterception of signaling is also supported by the MME. The MME alsoprovides the control plane function for mobility between LTE and 2G/3Gaccess networks with the S3 interface terminating at the MME from theSGSN. The MME also terminates the S6a interface towards the home HSS forroaming user equipments.

Component Carrier Structure in LTE

The downlink component carrier of a 3GPP LTE system is subdivided in thetime-frequency domain in so-called subframes. In 3GPP LTE each subframeis divided into two downlink slots as shown in FIG. 2 , wherein thefirst downlink slot comprises the control channel region (PDCCH region)within the first OFDM symbols. Each subframe consists of a give numberof OFDM symbols in the time domain (12 or 14 OFDM symbols in 3GPP LTE(Release 8)), wherein each OFDM symbol spans over the entire bandwidthof the component carrier. The OFDM symbols thus each consist of a numberof modulation symbols transmitted on respective subcarriers. In LTE, thetransmitted signal in each slot is described by a resource grid of

N_(RB)^(DL)N_(sc)^(RB)

subcarriers and

N_(symb)^(DL)

OFDM symbols.

N_(RB)^(DL)

is the number of resource blocks within the bandwidth. The quantity

N_(RB)^(DL)

depends on the downlink transmission bandwidth configured in the celland shall fulfill

N_(RB)^(min, DL) ≤ N_(RB)^(DL) ≤ N_(RB)^(max, DL), where N_(RB)^(min, DL) = 6 andN_(RB)^(max, DL) = 110

are respectively the smallest and the largest downlink bandwidths,supported by the current version of the specification.

N_(sc)^(RB)

is the number of subcarriers within one resource block. For normalcyclic prefix subframe structure,

N_(sc)^(RB) = 12 andN_(symb)^(DL) = 7

.

Assuming a multi-carrier communication system, e.g., employing OFDM, asfor example used in 3GPP Long Term Evolution (LTE), the smallest unit ofresources that can be assigned by the scheduler is one “resource block”.A physical resource block (PRB) is defined as consecutive OFDM symbolsin the time domain (e.g., 7 OFDM symbols) and consecutive subcarriers inthe frequency domain as exemplified in FIG. 2 (e.g., 12 subcarriers fora component carrier). In 3GPP LTE (Release 8), a physical resource blockthus consists of resource elements, corresponding to one slot in thetime domain and 180 kHz in the frequency domain (for further details onthe downlink resource grid, see for example 3GPP TS 36.211, “EvolvedUniversal Terrestrial Radio Access (E-UTRA); Physical Channels andModulation (Release 8)”, current version 13.0.0, section 6.2, availableat http://www.3gpp.org and incorporated herein by reference).

One subframe consists of two slots, so that there are 14 OFDM symbols ina subframe when a so-called “normal” CP (cyclic prefix) is used, and 12OFDM symbols in a subframe when a so-called “extended” CP is used. Forsake of terminology, in the following the time-frequency resourcesequivalent to the same consecutive subcarriers spanning a full subframeis called a “resource block pair”, or equivalent “RB pair” or “PRBpair”.

The term “component carrier” refers to a combination of several resourceblocks in the frequency domain. In future releases of LTE, the term“component carrier” is no longer used; instead, the terminology ischanged to “cell”, which refers to a combination of downlink andoptionally uplink resources. The linking between the carrier frequencyof the downlink resources and the carrier frequency of the uplinkresources is indicated in the system information transmitted on thedownlink resources.

Similar assumptions for the component carrier structure will apply tolater releases too.

Carrier Aggregation in LTE-A for Support of Wider Bandwidth

The frequency spectrum for IMT-Advanced was decided at the World Radiocommunication Conference 2007 (WRC-07). Although the overall frequencyspectrum for IMT-Advanced was decided, the actual available frequencybandwidth is different according to each region or country. Followingthe decision on the available frequency spectrum outline, however,standardization of a radio interface started in the 3rd GenerationPartnership Project (3GPP). At the 3GPP TSG RAN #39 meeting, the StudyItem description on “Further Advancements for E-UTRA (LTE-Advanced)” wasapproved. The study item covers technology components to be consideredfor the evolution of E-UTRA, e.g., to fulfill the requirements onIMT-Advanced.

The bandwidth that the LTE-Advanced system is able to support is 100MHz, while an LTE system can only support 20 MHz. Nowadays, the lack ofradio spectrum has become a bottleneck of the development of wirelessnetworks, and as a result it is difficult to find a spectrum band whichis wide enough for the LTE-Advanced system. Consequently, it is urgentto find a way to gain a wider radio spectrum band, wherein a possibleanswer is the carrier aggregation functionality.

In carrier aggregation, two or more component carriers are aggregated inorder to support wider transmission bandwidths up to 100 MHz. Severalcells in the LTE system are aggregated into one wider channel in theLTE-Advanced system which is wide enough for 100 MHz even though thesecells in LTE may be in different frequency bands.

All component carriers can be configured to be LTE Rel. 8/9 compatible,at least when the bandwidth of a component carrier does not exceed thesupported bandwidth of an LTE Rel. 8/9 cell. Not all component carriersaggregated by a user equipment may necessarily be Rel. 8/9 compatible.Existing mechanisms (e.g., barring) may be used to avoid Rel-8/9 userequipments to camp on a component carrier.

A user equipment may simultaneously receive or transmit on one ormultiple component carriers (corresponding to multiple serving cells)depending on its capabilities. An LTE-A Rel. 10 user equipment withreception and/or transmission capabilities for carrier aggregation cansimultaneously receive and/or transmit on multiple serving cells,whereas an LTE Rel. 8/9 user equipment can receive and transmit on asingle serving cell only, provided that the structure of the componentcarrier follows the Rel. 8/9 specifications.

Carrier aggregation is supported for both contiguous and non-contiguouscomponent carriers with each component carrier limited to a maximum of110 Resource Blocks in the frequency domain (using the 3GPP LTE (Release8/9) numerology).

It is possible to configure a 3GPP LTE-A (Release 10)-compatible userequipment to aggregate a different number of component carriersoriginating from the same eNodeB (base station) and of possiblydifferent bandwidths in the uplink and the downlink. The number ofdownlink component carriers that can be configured depends on thedownlink aggregation capability of the UE. Conversely, the number ofuplink component carriers that can be configured depends on the uplinkaggregation capability of the UE. It may currently not be possible toconfigure a mobile terminal with more uplink component carriers thandownlink component carriers. In a typical TDD deployment the number ofcomponent carriers and the bandwidth of each component carrier in uplinkand downlink is the same. Component carriers originating from the sameeNodeB need not provide the same coverage.

The spacing between center frequencies of contiguously aggregatedcomponent carriers shall be a multiple of 300 kHz. This is in order tobe compatible with the 100 kHz frequency raster of 3GPP LTE (Release8/9) and at the same time to preserve orthogonality of the subcarrierswith 15 kHz spacing. Depending on the aggregation scenario, the n × 300kHz spacing can be facilitated by insertion of a low number of unusedsubcarriers between contiguous component carriers.

The nature of the aggregation of multiple carriers is only exposed up tothe MAC layer. For both uplink and downlink there is one HARQ entityrequired in MAC for each aggregated component carrier. There is (in theabsence of SU-MIMO for uplink) at most one transport block per componentcarrier. A transport block and its potential HARQ retransmissions needto be mapped on the same component carrier.

When carrier aggregation is configured, the mobile terminal only has oneRRC connection with the network. At RRC connectionestablishment/re-establishment, one cell provides the security input(one ECGI, one PCI and one ARFCN) and the non-access stratum mobilityinformation (e.g., TAI) similarly as in LTE Rel. 8/9. After RRCconnection establishment/re-establishment, the component carriercorresponding to that cell is referred to as the downlink Primary Cell(PCell). There is always one and only one downlink PCell (DL PCell) andone uplink PCell (UL PCell) configured per user equipment in connectedstate. Within the configured set of component carriers, other cells arereferred to as Secondary Cells (SCells); with carriers of the SCellbeing the Downlink Secondary Component Carrier (DL SCC) and UplinkSecondary Component Carrier (UL SCC). Maximum five serving cells,including the PCell, can be configured for one UE.

MAC Layer/Entity, RRC Layer, Physical Layer

The LTE layer 2 user-plane/control-plane protocol stack comprises foursublayers, RRC, PDCP, RLC and MAC. The Medium Access Control (MAC) layeris the lowest sublayer in the Layer 2 architecture of the LTE radioprotocol stack and is defined by, e.g., the 3GPP technical standard TS36.321, current version 13.0.0. The connection to the physical layerbelow is through transport channels, and the connection to the RLC layerabove is through logical channels. The MAC layer therefore performsmultiplexing and demultiplexing between logical channels and transportchannels: the MAC layer in the transmitting side constructs MAC PDUs,known as transport blocks, from MAC SDUs received through logicalchannels, and the MAC layer in the receiving side recovers MAC SDUs fromMAC PDUs received through transport channels.

The MAC layer provides a data transfer service (see subclauses 5.4 and5.3 of TS 36.321 incorporated herein by reference) for the RLC layerthrough logical channels, which are either control logical channelswhich carry control data (e.g., RRC signaling) or traffic logicalchannels which carry user plane data. On the other hand, the data fromthe MAC layer is exchanged with the physical layer through transportchannels, which are classified as downlink or uplink. Data ismultiplexed into transport channels depending on how it is transmittedover the air.

The Physical layer is responsible for the actual transmission of dataand control information via the air interface, i.e., the Physical Layercarries all information from the MAC transport channels over the airinterface on the transmission side. Some of the important functionsperformed by the Physical layer include coding and modulation, linkadaptation (AMC), power control, cell search (for initialsynchronization and handover purposes) and other measurements (insidethe LTE system and between systems) for the RRC layer. The Physicallayer performs transmissions based on transmission parameters, such asthe modulation scheme, the coding rate (i.e., the modulation and codingscheme, MCS), the number of physical resource blocks, etc. Moreinformation on the functioning of the physical layer can be found in the3GPP technical standard 36.213 current version 13.0.0, incorporatedherein by reference.

The Radio Resource Control (RRC) layer controls communication between aUE and an eNB at the radio interface and the mobility of a UE movingacross several cells. The RRC protocol also supports the transfer of NASinformation. For UEs in RRC_IDLE, RRC supports notification from thenetwork of incoming calls. RRC connection control covers all proceduresrelated to the establishment, modification and release of an RRCconnection, including paging, measurement configuration and reporting,radio resource configuration, initial security activation, andestablishment of Signaling Radio Bearer (SRBs) and of radio bearerscarrying user data (Data Radio Bearers, DRBs).

The radio link control (RLC) sublayer comprises mainly ARQ functionalityand supports data segmentation and concatenation, i.e., RLC layerperforms framing of RLC SDUs to put them into the size indicated by theMAC layer. The latter two minimize the protocol overhead independentlyfrom the data rate. The RLC layer is connected to the MAC layer vialogical channels. Each logical channel transports different types oftraffic. The layer above RLC layer is typically the PDCP layer, but insome cases it is the RRC layer, i.e., RRC messages transmitted on thelogical channels BCCH (Broadcast Control Channel), PCCH (Paging ControlChannel) and CCCH (Common Control Channel) do not require securityprotection and thus go directly to the RLC layer, bypassing the PDCPlayer. The main services and functions of the RLC sublayer include:

-   Transfer of upper layer PDUs supporting AM, UM or TM data transfer;-   Error Correction through ARQ;-   Segmentation according to the size of the TB;-   Resegmentation when necessary (e.g., when the radio quality, i.e.,    the supported TB size changes);-   Concatenation of SDUs for the same radio bearer is FFS;-   In-sequence delivery of upper layer PDUs;-   Duplicate Detection;-   Protocol error detection and recovery;-   SDU discard;-   Reset.

The ARQ functionality provided by the RLC layer will be discussed inmore detail at a later part.

Uplink Access Scheme for LTE

For uplink transmission, power-efficient user-terminal transmission isnecessary to maximize coverage. Single-carrier transmission combinedwith FDMA with dynamic bandwidth allocation has been chosen as theevolved UTRA uplink transmission scheme. The main reason for thepreference for single-carrier transmission is the lower peak-to-averagepower ratio (PAPR), compared to multi-carrier signals (OFDMA), and thecorresponding improved power-amplifier efficiency and improved coverage(higher data rates for a given terminal peak power). During each timeinterval, eNodeB assigns users a unique time/frequency resource fortransmitting user data, thereby ensuring intra-cell orthogonality. Anorthogonal access in the uplink promises increased spectral efficiencyby eliminating intra-cell interference. Interference due to multipathpropagation is handled at the base station (eNodeB), aided by insertionof a cyclic prefix in the transmitted signal.

The basic physical resource used for data transmission consists of afrequency resource of size BWgrant during one time interval, e.g., asubframe, onto which coded information bits are mapped. It should benoted that a subframe, also referred to as transmission time interval(TTI), is the smallest time interval for user data transmission. It ishowever possible to assign a frequency resource BWgrant over a longertime period than one TTI to a user by concatenation of subframes.

Layer 1 / Layer 2 Control Signaling

In order to inform the scheduled users about their allocation status,transport format, and other transmission-related information (e.g., HARQinformation, transmit power control (TPC) commands), L1/L2 controlsignaling is transmitted on the downlink along with the data. L1/L2control signaling is multiplexed with the downlink data in a subframe,assuming that the user allocation can change from subframe to subframe.It should be noted that user allocation might also be performed on a TTI(Transmission Time Interval) basis, where the TTI length can be amultiple of the subframes. The TTI length may be fixed in a service areafor all users, may be different for different users, or may even bydynamic for each user. Generally, the L1/2 control signaling needs onlybe transmitted once per TTI. Without loss of generality, the followingassumes that a TTI is equivalent to one subframe.

The L1/L2 control signaling is transmitted on the Physical DownlinkControl Channel (PDCCH). A PDCCH carries a message as a Downlink ControlInformation (DCI), which in most cases includes resource assignments andother control information for a mobile terminal or groups of UEs.Several PDCCHs can be transmitted in one subframe.

Generally, the information sent in the L1/L2 control signaling forassigning uplink or downlink radio resources (particularly LTE(-A)Release 10) can be categorized to the following items:

-   User identity, indicating the user that is allocated. This is    typically included in the checksum by masking the CRC with the user    identity;-   Resource allocation information, indicating the resources (e.g.,    Resource Blocks, RBs) on which a user is allocated. Alternatively,    this information is termed resource block assignment (RBA). Note,    that the number of RBs on which a user is allocated can be dynamic;-   Carrier indicator, which is used if a control channel transmitted on    a first carrier assigns resources that concern a second carrier,    i.e., resources on a second carrier or resources related to a second    carrier; (cross carrier scheduling);-   Modulation and coding scheme that determines the employed modulation    scheme and coding rate;-   HARQ information, such as a new data indicator (NDI) and/or a    redundancy version (RV) that is particularly useful in    retransmissions of data packets or parts thereof;-   Power control commands to adjust the transmit power of the assigned    uplink data or control information transmission;-   Reference signal information such as the applied cyclic shift and/or    orthogonal cover code index, which are to be employed for    transmission or reception of reference signals related to the    assignment;-   Uplink or downlink assignment index that is used to identify an    order of assignments, which is particularly useful in TDD systems;-   Hopping information, e.g., an indication whether and how to apply    resource hopping in order to increase the frequency diversity;-   CSI request, which is used to trigger the transmission of channel    state information in an assigned resource; and-   Multi-cluster information, which is a flag used to indicate and    control whether the transmission occurs in a single cluster    (contiguous set of RBs) or in multiple clusters (at least two    non-contiguous sets of contiguous RBs). Multi-cluster allocation has    been introduced by 3GPP LTE-(A) Release 10.

It is to be noted that the above listing is non-exhaustive, and not allmentioned information items need to be present in each PDCCHtransmission depending on the DCI format that is used.

Downlink control information occurs in several formats that differ inoverall size and also in the information contained in their fields asmentioned above. The different DCI formats that are currently definedfor LTE are as follows and described in detail in 3GPP TS 36.212,“Multiplexing and channel coding”, section 5.3.3.1 (current versionv13.0.0 available at http://www.3gpp.org and incorporated herein byreference). For instance, the following DCI Formats can be used to carrya resource grant for the uplink.

Format 0: DCI Format 0 is used for the transmission of resource grantsfor the PUSCH, using single-antenna port transmissions in uplinktransmission mode 1 or 2.

Format 4: DCI format 4 is used for the scheduling of the PUSCH, usingclosed-loop spatial multiplexing transmissions in uplink transmissionmode 2.

The 3GPP technical standard TS 36.212, current version 13.0.0, definesin subclause 5.4.3, incorporated herein by reference, controlinformation for the sidelink.

LTE Device to Device (D2D) Proximity Services (ProSe)

Proximity-based applications and services represent an emergingsocial-technological trend. The identified areas include servicesrelated to commercial services and Public Safety that would be ofinterest to operators and users. The introduction of a ProximityServices (ProSe) capability in LTE would allow the 3GPP industry toserve this developing market and will, at the same time, serve theurgent needs of several Public Safety communities that are jointlycommitted to LTE.

Device-to-Device (D2D) communication is a technology componentintroduced by LTE-Rel.12, which allows D2D as an underlay to thecellular network to increase the spectral efficiency. For example, ifthe cellular network is LTE, all data-carrying physical channels useSC-FDMA for D2D signaling. In D2D communications, user equipmentstransmit data signals to each other over a direct link using thecellular resources instead of through the radio base station. Throughoutthe disclosure the terms “D2D”, “ProSe” and “sidelink” areinterchangeable.

The D2D communication in LTE is focusing on two areas: Discovery andCommunication.

ProSe (Proximity-based Services) Direct Discovery is defined as theprocedure used by the ProSe-enabled UE to discover other ProSe-enabledUE(s) in its proximity using E-UTRA direct radio signals via the PC5interface.

In D2D communication, UEs transmit data signals to each other over adirect link using the cellular resources instead of through the basestation (BS). D2D users communicate directly while remaining controlledunder the BS, i.e., at least when being in coverage of an eNB.Therefore, D2D can improve system performance by reusing cellularresources.

It is assumed that D2D operates in the uplink LTE spectrum (in the caseof FDD) or uplink sub-frames of the cell giving coverage (in case ofTDD, except when out of coverage). Furthermore, D2Dtransmission/reception does not use full duplex on a given carrier. Fromindividual UE perspective, on a given carrier D2D signal reception andLTE uplink transmission do not use full duplex, i.e., no simultaneousD2D signal reception and LTE UL transmission is possible.

In D2D communication, when one particular UE1 has a role of transmission(transmitting user equipment or transmitting terminal), UE1 sends data,and another UE2 (receiving user equipment) receives it. UE1 and UE2 canchange their transmission and reception role. The transmission from UE1can be received by one or more UEs like UE2.

ProSe Direct Communication Layer-2 Link

In brief, ProSe direct one-to-one communication is realized byestablishing a secure layer-2 link over PC5 between two UEs. Each UE hasa Layer-2 ID for unicast communication that is included in the SourceLayer-2 ID field of every frame that it sends on the layer-2 link and inthe Destination Layer-2 ID of every frame that it receives on thelayer-2 link. The UE needs to ensure that the Layer-2 ID for unicastcommunication is at least locally unique. So the UE should be preparedto handle Layer-2 ID conflicts with adjacent UEs using unspecifiedmechanisms (e.g., self-assign a new Layer-2 ID for unicast communicationwhen a conflict is detected). The layer-2 link for ProSe directcommunication one-to-one is identified by the combination of the Layer-2IDs of the two UEs. This means that the UE can engage in multiplelayer-2 links for ProSe direct communication one-to-one using the sameLayer-2 ID.

ProSe direct communication one-to-one is composed of the followingprocedures as explained in detail in TR 23.713 current version v 13.0.0section 7.1.2 incorporated herein by reference:

-   Establishment of a secure layer-2 link over PC5.-   IP address/prefix assignment.-   Layer-2 link maintenance over PC5.-   Layer-2 link release over PC5.

FIG. 3 illustrates how to establish a secure layer-2 link over the PC5interface.

1. UE-1 sends a Direct Communication Request message to UE-2 in order totrigger mutual authentication. The link initiator (UE-1) needs to knowthe Layer-2 ID of the peer (UE-2) in order to perform step 1. As anexample, the link initiator may learn the Layer-2 ID of the peer byexecuting a discovery procedure first or by having participated in ProSeone-to-many communication including the peer.

2. UE-2 initiates the procedure for mutual authentication. Thesuccessful completion of the authentication procedure completes theestablishment of the secure layer-2 link over PC5.

UEs engaging in isolated (non-relay) one-to-one communication may alsouse link-local addresses. The PC5 Signaling Protocol shall supportkeep-alive functionality that is used to detect when the UEs are not inProSe Communication range, so that they can proceed with implicitlayer-2 link release. The Layer-2 link release over the PC5 can beperformed by using a Disconnect Request message transmitted to the otherUE, which also deletes all associated context data. Upon reception ofthe Disconnect Request message, the other UE responds with a DisconnectResponse message and deletes all context data associated with thelayer-2 link.

ProSe Direct Communication Related Identities

3GPP TS 36.300, current version 13.2.0, defines in subclause 8.3 thefollowing identities to use for ProSe Direct Communication:

-   SL-RNTI: Unique identification used for ProSe Direct Communication    Scheduling;-   Source Layer-2 ID: Identifies the sender of the data in sidelink    ProSe Direct Communication. The Source Layer-2 ID is 24 bits long    and is used together with ProSe Layer-2 Destination ID and LCID for    identification of the RLC UM entity and PDCP entity in the receiver;-   Destination Layer-2 ID: Identifies the target of the data in    sidelink ProSe Direct Communication. The Destination Layer-2 ID is    24 bits long and is split in the MAC layer into two bit strings:    -   One bit string is the LSB part (8 bits) of Destination Layer-2        ID and forwarded to the physical layer as Sidelink Control        Layer-1 ID. This identifies the target of the intended data in        Sidelink Control and is used for filtering packets at the        physical layer.    -   Second bit string is the MSB part (16 bits) of the Destination        Layer -2 ID and is carried within the MAC header. This is used        for filtering packets at the MAC layer.

No Access Stratum signaling is required for group formation and toconfigure Source Layer-2 ID, Destination Layer-2 ID and Sidelink ControlL1 ID in the UE. These identities are either provided by a higher layeror derived from identities provided by a higher layer. In case ofgroupcast and broadcast, the ProSe UE ID provided by the higher layer isused directly as the Source Layer-2 ID, and the ProSe Layer-2 Group IDprovided by the higher layer is used directly as the Destination Layer-2ID in the MAC layer. In case of one-to-one communications, higher layerprovides Source Layer-2 ID and Destination Layer-2 ID.

Radio Resource Allocation for Proximity Services

From the perspective of a transmitting UE, a Proximity-Services-enabledUE (ProSe-enabled UE) can operate in two modes for resource allocation:

Mode 1 refers to the eNB-scheduled resource allocation, where the UErequests transmission resources from the eNB (or Release-10 relay node),and the eNodeB (or Release-10 relay node) in turn schedules theresources used by a UE to transmit direct data and direct controlinformation (e.g., Scheduling Assignment). The UE needs to beRRC_CONNECTED in order to transmit data. In particular, the UE sends ascheduling request (D-SR or Random Access) to the eNB followed by abuffer status report (BSR) in the usual manner (see also followingchapter “Transmission procedure for D2D communication”). Based on theBSR, the eNB can determine that the UE has data for a ProSe DirectCommunication transmission and can estimate the resources needed fortransmission.

On the other hand, Mode 2 refers to the UE-autonomous resourceselection, where a UE on its own selects resources (time and frequency)from resource pool(s) to transmit direct data and direct controlinformation (i.e., SA). One resource pool is defined, e.g., by thecontent of SIB 18, namely by the field commTxPoolNormalCommon, thisparticular resource pool being broadcast in the cell and then commonlyavailable for all UEs in the cell still in RRC_Idle state. Effectively,the eNB may define up to four different instances of said pool,respectively four resource pools for the transmission of SA messages anddirect data. However, in Rel-12 a UE shall always use the first resourcepool defined in the list, even if it was configured with multipleresource pools. This restriction was removed for Rel-13, i.e., a UE cantransmit on multiple of the configured resource pools within one SCperiod. How the UE selects the resource pools for transmission isfurther outlined below (further specified in TS36.321).

As an alternative, another resource pool can be defined by the eNB andsignaled in SIB 18, namely by using the field commTxPoolExceptional,which can be used by the UEs in exceptional cases.

What resource allocation mode a UE is going to use is configurable bythe eNB. Furthermore, what resource allocation mode a UE is going to usefor D2D data communication may also depend on the RRC state, i.e.,RRC_IDLE or RRC_CONNECTED, and the coverage state of the UE, i.e.,in-coverage, out-of-coverage. A UE is considered in-coverage if it has aserving cell (i.e., the UE is RRC_CONNECTED or is camping on a cell inRRC_IDLE).

The following rules with respect to the resource allocation mode applyfor the UE:

-   If the UE is out-of-coverage, it can only use Mode 2;-   If the UE is in-coverage, it may use Mode 1 if the eNB configures it    accordingly;-   If the UE is in-coverage, it may use Mode 2 if the eNB configures it    accordingly;-   When there are no exceptional conditions, UE may change from Mode 1    to Mode 2 or vice-versa only if it is configured by eNB to do so. If    the UE is in-coverage, it shall use only the mode indicated by eNB    configuration unless one of the exceptional cases occurs;-   The UE considers itself to be in exceptional conditions, e.g., while    T311 or T301 is running;-   When an exceptional case occurs the UE is allowed to use Mode 2    temporarily even though it was configured to use Mode 1.

While being in the coverage area of an E-UTRA cell, the UE shall performProSe Direct Communication Transmission on the UL carrier only on theresources assigned by that cell, even if resources of that carrier havebeen pre-configured, e.g., in UICC (Universal Integrated Circuit Card).

For UEs in RRC_IDLE the eNB may select one of the following options:

-   The eNB may provide a Mode 2 transmission resource pool in SIB. UEs    that are authorized for ProSe Direct Communication use these    resources for ProSe Direct Communication in RRC_IDLE;-   The eNB may indicate in SIB that it supports D2D but does not    provide resources for ProSe Direct Communication. UEs need to enter    RRC_CONNECTED to perform ProSe Direct Communication transmission.

For UEs in RRC_CONNECTED:

-   A UE in RRC_CONNECTED that is authorized to perform ProSe Direct    Communication transmission, indicates to the eNB that it wants to    perform ProSe Direct Communication transmissions when it needs to    perform ProSe Direct Communication transmission;-   The eNB validates whether the UE in RRC_CONNECTED is authorized for    ProSe Direct Communication transmission using the UE context    received from MME;-   The eNB may configure a UE in RRC_CONNECTED by dedicated signaling    with a Mode-2 resource allocation transmission resource pool that    may be used without constraints while the UE is RRC_CONNECTED.    Alternatively, the eNB may configure a UE in RRC_CONNECTED by    dedicated signaling with a Mode 2 resource allocation transmission    resource pool which the UE is allowed to use only in exceptional    cases and rely on Mode 1 otherwise.

The resource pool for Scheduling Assignment when the UE is out ofcoverage can be configured as below:

-   The resource pool used for reception is pre-configured.-   The resource pool used for transmission is pre-configured.

The resource pool for Scheduling Assignment when the UE is in coveragecan be configured as below:

-   The resource pool used for reception is configured by the eNB via    RRC, in dedicated or broadcast signaling.-   The resource pool used for transmission is configured by the eNB via    RRC if Mode 2 resource allocation is used-   The SCI (Sidelink Control Information) resource pool (also referred    to as Scheduling Assignment, SA, resource pool) used for    transmission is not known to the UE if Mode 1 resource allocation is    used.-   The eNB schedules the specific resource(s) to use for Sidelink    Control Information (Scheduling Assignment) transmission if Mode 1    resource allocation is used. The specific resource assigned by the    eNB is within the resource pool for reception of SCI that is    provided to the UE.

FIG. 4 illustrates the use of transmission/reception resources foroverlay (LTE) and underlay (D2D) system.

Basically, the eNodeB controls whether UE may apply the Mode 1 or Mode 2transmission. Once the UE knows its resources where it can transmit (orreceive) D2D communication, it uses the corresponding resources only forthe corresponding transmission/reception. For example, in FIG. 4 the D2Dsubframes will only be used to receive or transmit the D2D signals.Since the UE as a D2D device would operate in Half Duplex mode, it caneither receive or transmit the D2D signals at any point of time.Similarly, the other subframes illustrated in FIG. 4 can be used for LTE(overlay) transmissions and/or reception.

Transmission Procedure for D2D Communication

The D2D data transmission procedure differs depending on the resourceallocation mode. As described above for Mode 1, the eNB explicitlyschedules the resources for the Scheduling Assignment and the D2D datacommunication after a corresponding request from the UE. Particularly,the UE may be informed by the eNB that D2D communication is generallyallowed, but that no Mode 2 resources (i.e., resource pool) areprovided; this may be done, e.g., with the exchange of the D2Dcommunication Interest Indication by the UE and the correspondingresponse, D2D Communication Response, where the corresponding exemplaryProseCommConfig information element would not include thecommTxPoolNormalCommon, meaning that a UE that wants to start directcommunication involving transmissions has to request E-UTRAN to assignresources for each individual transmission. Thus, in such a case, the UEhas to request the resources for each individual transmission, and inthe following the different steps of the request/grant procedure areexemplarily listed for this Mode 1 resource allocation:

-   Step 1: UE sends SR (Scheduling Request) to eNB via PUCCH;-   Step 2: eNB grants UL resource (for UE to send BSR) via PDCCH,    scrambled by C-RNTI;-   Step 3: UE sends D2D BSR indicating the buffer status via PUSCH;-   Step 4: eNB grants D2D resource (for UE to send data) via PDCCH,    scrambled by D2D-RNTI.-   Step 5: D2D Tx UE transmits SA/D2D data according to grant received    in step 4.

A Scheduling Assignment (SA), also termed SCI (Sidelink ControlInformation) is a compact (low-payload) message containing controlinformation, e.g., pointer(s) to time-frequency resources, modulationand coding scheme and Group Destination ID for the corresponding D2Ddata transmission. An SCI transports the sidelink scheduling informationfor one (ProSE) destination ID. The content of the SA (SCI) is basicallyin accordance with the grant received in Step 4 above. The D2D grant andSA content (i.e., SCI content) are defined in the 3GPP technicalstandard 36.212, current version 13.0.0, subclause 5.4.3, incorporatedherein by reference, defining in particular the SCI format 0 (seecontent of SCI format 0 above).

On the other hand, for Mode 2 resource allocation, above steps 1-4 arebasically not necessary, and the UE autonomously selects resources forthe SA and D2D data transmission from the transmission resource pool(s)configured and provided by the eNB.

FIG. 5 exemplarily illustrates the transmission of the SchedulingAssignment and the D2D data for two UEs, UE-1 and UE-2, where theresources for sending the scheduling assignments are periodic, and theresources used for the D2D data transmission are indicated by thecorresponding Scheduling Assignment.

FIG. 6 illustrates the D2D communication timing for Mode 2, autonomousscheduling, during one SA/data period, also known as SC period, SidelinkControl period. FIG. 7 illustrates the D2D communication timing for Mode1, eNB-scheduled allocation during one SA/data period. A SC period isthe time period consisting of transmission of a Scheduling Assignmentand its corresponding data. As can be seen from FIG. 6 , the UEtransmits after an SA-offset time, a Scheduling Assignment using thetransmission pool resources for scheduling assignments for Mode 2,SA_Mode2_Tx_pool. The 1st transmission of the SA is followed, e.g., bythree retransmissions of the same SA message. Then, the UE starts theD2D data transmission, i.e., more in particular the T-RPTbitmap/pattern, at some configured offset (Mode2data_offset) after thefirst subframe of the SA resource pool (given by the SA_offset). One D2Ddata transmission of a MAC PDU (i.e., a transport block) consists of its1st initial transmission and several retransmissions. For theillustration of FIG. 6 (and of FIG. 7 ) it is assumed that threeretransmissions are performed (i.e., 2nd, 3rd, and 4th transmission ofthe same MAC PDU). The Mode2 T-RPT Bitmap (time resource pattern oftransmission, T-RPT) basically defines the timing of the MAC PDUtransmission (1st transmission) and its retransmissions (2^(nd), 3^(rd),and 4^(th) transmission). The SA pattern basically defines the timing ofthe SA’s initial transmission and its retransmissions (2^(nd), 3^(rd),and 4^(th) transmission).

As currently specified in the standard, for one sidelink grant, e.g.,either sent by the eNB or selected by the UE itself, , the UE cantransmit multiple transport blocks, MAC PDUs, (only one per subframe(TTI), i.e., one after the other), however to only one ProSe destinationgroup. Also the retransmissions of one transport block must be finishedbefore the first transmission of the next transport block starts, i.e.,only one HARQ process is used per sidelink grant for the transmission ofthe multiple transport blocks. Furthermore, the UE can have and useseveral sidelink grants per SC period, but a different ProSe destinationbe selected for each of them. Thus, in one SC period the UE can transmitdata to one ProSe destination only one time.

As apparent from FIG. 7 , for the eNB-scheduled resource allocation mode(Mode 1), the D2D data transmission, i.e., more in particular the T-RPTpattern/bitmap, starts in the next UL subframe after the last SAtransmission repetition in the SA resource pool. As explained alreadyfor FIG. 6 , the Model T-RPT Bitmap (time resource pattern oftransmission, T-RPT) basically defines the timing of the MAC PDUtransmission (1st transmission) and its retransmissions (2nd, 3rd, and4th transmission).

The sidelink data transmission procedure can be found in the 3GPPstandard document TS 36.321 v13.0.0, section 5.14, incorporated hereinby reference. Therein, the Mode-2 autonomous resource selection isdescribed in detail, differentiating between being configured with asingle radio resource pool or multiple radio resource pools. Thefollowing steps are taken from said section of TS 36.321, assumingMode-2 autonomous resource selection:

In order to transmit on the SL-SCH (sidelink shared channel) the MACentity must have at least one sidelink grant. Sidelink grants areselected as follows:

-   If the MAC entity is configured by upper layers to transmit using    one or multiple pool(s) of resources and more data is available in    STCH (sidelink traffic channel) than can be transmitted in the    current SC period, the MAC entity shall for each sidelink grant to    be selected:    -   if configured by upper layers to use a single pool of resources:        select that pool of resources for use;    -   else, if configured by upper layers to use multiple pools of        resources: select a pool of resources for use from the pools of        resources

    configured by upper layers whose associated priority list includes    the priority of the highest priority of the sidelink logical channel    in the MAC PDU to be transmitted;-   NOTE: If more than one pool of resources has an associated priority    list which includes the priority of the sidelink logical channel    with the highest priority in the MAC PDU to be transmitted, it is    left for UE implementation which one of those pools of resources to    select.-   randomly select the time and frequency resources for SL-SCH and SCI    of a sidelink grant from the selected resource pool. The random    function shall be such that each of the allowed selections can be    chosen with equal probability;-   use the selected sidelink grant to determine the set of subframes in    which transmission of SCI and transmission of first transport block    occur according to subclause 14.2.1 of TS 36.213 incorporated herein    by reference (this step refers to the selection of a T-RPT and a SA    pattern, as explained in connection with FIG. 7 );-   consider the selected sidelink grant to be a configured sidelink    grant occurring in those subframes starting at the beginning of the    first available SC Period which starts at least 4 subframes after    the subframe in which the sidelink grant was selected;-   clear the configured sidelink grant at the end of the corresponding    SC Period;-   NOTE: Retransmissions on SL-SCH cannot occur after the configured    sidelink grant has been cleared.-   NOTE: If the MAC entity is configured by upper layers to transmit    using one or multiple pool(s) of resources, it is left for UE    implementation how many sidelink grants to select within one SC    period taking the number of sidelink processes into account.

The MAC entity shall for each subframe:

-   if the MAC entity has a configured sidelink grant occurring in this    subframe:    -   if the configured sidelink grant corresponds to transmission of        SCI:        -   instruct the physical layer to transmit SCI corresponding to            the configured sidelink grant.        -   else if the configured sidelink grant corresponds to            transmission of first transport block:            -   deliver the configured sidelink grant and the associated                HARQ information to the Sidelink HARQ Entity for this                subframe.-   NOTE: If the MAC entity has multiple configured grants occurring in    one subframe and if not all of them can be processed due to the    single-cluster SC-FDM restriction, it is left for UE implementation    which one of these to process according to the procedure above.

The above text taken from the 3GPP technical standard can be clarifiedfurther. For example, the step of randomly selecting the time andfrequency resources is random as to which particular time/frequencyresources are chosen but is, e.g., not random as to the amount oftime/frequency resources selected in total. The amount of resourcesselected from the resource pool depends on the amount of data that is tobe transmitted with said sidelink grant to be selected autonomously. Inturn, the amount of data that is to be transmitted depends on theprevious step of selecting the ProSe destination group and thecorresponding amount of data ready for transmission destined to saidProSe destination group. As described later in the sidelink LCPprocedure, the ProSe destination is selected first.

Furthermore, the sidelink process associated with the sidelink HARQentity is responsible for instructing the physical layer to generate andperform a transmission accordingly, as apparent from section 5.14.1.2.2of 3GPP TS 36.321 v13.0.0, incorporated herein by reference. In brief,after determining the sidelink grant and the sidelink data to transmit,the physical layer takes care that the sidelink data is actuallytransmitted, based on the sidelink grant and the necessary transmissionparameters.

What is discussed above is the current status of the 3GPP standard forthe D2D communication. However, it should be noted that there has beenongoing discussions on how to further improve and enhance the D2Dcommunication which will likely result in that some changes areintroduced to the D2D communication in future releases. The presentdisclosure as will be described later shall be also applicable to thoselater releases.

ProSe Network Architecture and ProSe Entities

FIG. 8 illustrates a high-level exemplary architecture for a non-roamingcase, including different ProSe applications in the respective UEs A andB, as well as a ProSe Application Server and ProSe function in thenetwork. The example architecture of FIG. 8 is taken from TS 23.303v.13.2.0 chapter 4.2 “Architectural Reference Model” incorporated hereinby reference.

The functional entities are presented and explained in detail in TS23.303 subclause 4.4 “Functional Entities” incorporated herein byreference. The ProSe function is the logical function that is used fornetwork-related actions required for ProSe and plays different roles foreach of the features of ProSe. The ProSe function is part of the 3GPP’sEPC and provides all relevant network services like authorization,authentication, data handling, etc., related to proximity services. ForProSe direct discovery and communication, the UE may obtain a specificProSe UE identity, other configuration information, as well asauthorization from the ProSe function over the PC3 reference point.There can be multiple ProSe functions deployed in the network, althoughfor ease of illustration a single ProSe function is presented. The ProSefunction consists of three main sub-functions that perform differentroles depending on the ProSe feature: Direct Provision Function (DPF),Direct Discovery Name Management Function, and EPC-level DiscoveryFunction. The DPF is used to provision the UE with the necessaryparameters to use ProSe Direct Discovery and ProSe Direct Communication.

The term “UE” used in said connection refers to a ProSe-enabled UEsupporting ProSe functionality, such as:

-   Exchange of ProSe control information between ProSe-enabled UE and    the ProSe Function over PC3 reference point.-   Procedures for open ProSe Direct Discovery of other ProSe-enabled    UEs over PC5 reference point.-   Procedures for one-to-many ProSe Direct Communication over PC5    reference point.-   Procedures to act as a ProSe UE-to-Network Relay. The Remote UE    communicates with the ProSe UE-to-Network Relay over PC5 reference    point. The ProSe UE-to Network Relay uses layer-3 packet forwarding.-   Exchange of control information between ProSe UEs over PC5 reference    point, e.g., for UE-to-Network Relay detection and ProSe Direct    Discovery.-   Exchange of ProSe control information between another ProSe-enabled    UE and the ProSe Function over PC3 reference point. In the ProSe    UE-to-Network Relay case the Remote UE will send this control    information over PC5 user plane to be relayed over the LTE-Uu    interface towards the ProSe Function.-   Configuration of parameters (e.g., including IP addresses, ProSe    Layer-2 Group IDs, Group security material, radio resource    parameters). These parameters can be pre-configured in the UE, or,    if in coverage, provisioned by signaling over the PC3 reference    point to the ProSe Function in the network.

The ProSe Application Server supports the Storage of EPC ProSe User IDs,and ProSe Function IDs, and the mapping of Application Layer User IDsand EPC ProSe User IDs. The ProSe Application Server (AS) is an entityoutside the scope of 3GPP. The ProSe application in the UE communicateswith the ProSe AS via the application-layer reference point PC1. TheProSe AS is connected to the 3GPP network via the PC2 reference point.

Vehicular Communication – V2X Services

A new study item has been set up in the 3GPP to consider the usefulnessof new LTE features to the automotive industry - including ProximityService (ProSE) and LTE-based broadcast services. ProSe functionality isthus considered as offering a good foundation for the V2X services.Connected vehicle technologies aim to tackle some of the biggestchallenges in the surface transportation industry, such as safety,mobility, and traffic efficiency.

V2X communication is the passing of information from a vehicle to anyentity that may affect the vehicle, and vice versa. This informationexchange can be used to improve safety, mobility and environmentalapplications to include driver assistance vehicle safety, speedadaptation and warning, emergency response, travel information,navigation, traffic operations, commercial fleet planning and paymenttransactions.

LTE support for V2X services contains 3 types of different use caseswhich are the following:

-   V2V: covering LTE-based communication between vehicles.-   V2P: covering LTE-based communication between a vehicle and a device    carried by an individual (e.g., handheld terminal carried by a    pedestrian, cyclist, driver or passenger).-   V2I: covering LTE-based communication between a vehicle and a road    side unit.

These three types of V2X can use “co-operative awareness” to providemore intelligent services for end-users. This means that transportentities, such as vehicles, roadside infrastructure, and pedestrians,can collect knowledge of their local environment (e.g., informationreceived from other vehicles or sensor equipment in proximity) toprocess and share that knowledge in order to provide more intelligentservices, such as cooperative collision warning or autonomous driving.

With regard to V2V communication, E-UTRAN allows such UEs that are inproximity of each other to exchange V2V-related information usingE-UTRA(N) when permission, authorization and proximity criteria arefulfilled. The proximity criteria can be configured by the MNO (MobileNetwork Operator). However, UEs supporting V2V Service can exchange suchinformation when served by or not served by E-UTRAN which supports V2XService.

The UE supporting V2V applications transmits application layerinformation (e.g., about its location, dynamics, and attributes as partof the V2V Service). The V2V payload must be flexible in order toaccommodate different information contents, and the information can betransmitted periodically according to a configuration provided by theMNO.

V2V is predominantly broadcast-based; V2V includes the exchange ofV2V-related application information between distinct UEs directlyand/or, due to the limited direct communication range of V2V, theexchange of V2V-related application information between distinct UEs viainfrastructure supporting V2X Service, e.g., RSU, application server,etc.

With regard to V2I communication, the UE supporting V2I applicationssends application layer information to the Road Side Unit, which in turncan send application layer information to a group of UEs or a UEsupporting V2I applications.

V2N (Vehicle to Network, eNB/CN) is also introduced where one party is aUE and the other party is a serving entity, both supporting V2Napplications and communicating with each other via LTE network.

With regard to V2P communication, E-UTRAN allows such UEs that are inproximity of each other to exchange V2P-related information usingE-UTRAN when permission, authorization and proximity criteria arefulfilled. The proximity criteria can be configured by the MNO. However,UEs supporting V2P Service can exchange such information even when notserved by E-UTRAN which supports V2X Service.

The UE supporting V2P applications transmits application layerinformation. Such information can be broadcast by a vehicle with UEsupporting V2X Service (e.g., warning to pedestrian), and/or by apedestrian with UE supporting V2X Service (e.g., warning to vehicle).

V2P includes the exchange of V2P-related application information betweendistinct UEs (one for vehicle and the other for pedestrian) directlyand/or, due to the limited direct communication range of V2P, theexchange of V2P-related application information between distinct UEs viainfrastructure supporting V2X Service, e.g., RSU, application server,etc.

For this new study item V2X, 3GPP has provided particular terms anddefinition in TR 21.905, current version 13.0.0, which can be reused forthis application.

Road Side Unit (RSU): An entity supporting V2I Service that can transmitto, and receive from a UE using V2I application. An RSU can beimplemented in an eNB or a stationary UE.

V2I Service: A type of V2X Service, where one party is a UE and theother party is an RSU both using V2I application.

V2N Service: A type of V2X Service, where one party is a UE and theother party is a serving entity, both using V2N applications andcommunicating with each other via LTE network entities.

V2P Service: A type of V2X Service, where both parties of thecommunication are UEs using V2P application.

V2V Service: A type of V2X Service, where both parties of thecommunication are UEs using V2V application.

V2X Service: A type of communication service that involves atransmitting or receiving UE using V2V application via 3GPP transport.Based on the other party involved in the communication, it can befurther divided into V2V Service, V2I Service, V2P Service, and V2NService.

The 3GPP has also agreed on some potential requirements for V2Xcommunication, where some of the relevant ones will be presented in thefollowing.

[CPR The E-UTRA(N) shall be able to support a maximum frequency of 10V2X messages per second per V2X entity (e.g., UE and RSU).

[CPR For particular usage (i.e., pre-crash sensing) only, the E-UTRA(N)should be capable of transferring V2X messages between two UEssupporting V2V Service with a maximum latency of 20 ms.

[CPR The 3GPP network should make available any supported positionalaccuracy improvement techniques (e.g., DGPS and/or OTDOA) in a resourceefficient way to a subscribed UE supporting V2X Service.

[CPR The 3GPP system shall be able to vary the transmission rate andcoverage area based on service conditions (e.g., UE speed, UE density).

[CPR The E-UTRAN shall be capable of transferring V2X messages betweenUEs supporting V2V Service with a maximum relative velocity of 280 km/h.

Vehicular communication will presumably be based on ProSe directcommunication. However, the usual Rel. 12 D2D resource allocation mightnot be sufficient for the new V2X usage scenarios. In particular, asexplained before, randomization is a basic principle used in D2Dcommunication; specifically, for Mode 2 where the UE)(s) autonomouslyand randomly select radio resources for communication from configuredradio resource pools. In D2D-based vehicular communication,time-and-frequency resource collision can become a more serious problem,e.g., because the packet size may increase (due to vehicularapplications possibly transmitting often and large amounts of data) andthere is a large number of UEs in the target coverage particularly fordense UE-deployment scenarios such as in urban scenarios.

Correspondingly, the currently envisaged resource allocation forvehicular communication based on D2D might not be optimal and willrequire various adaptations to the new usage scenarios.

BRIEF SUMMARY

Non-limiting and exemplary embodiments provide an improved resourceallocation method for vehicular communication for a vehicular mobileterminal.

The independent claims provide non-limiting and exemplary embodiments.Advantageous embodiments are subject to the dependent claims.

According to several aspects described herein, the determination ofradio resources to be used by a vehicular mobile terminal forcommunicating with another mobile terminal (be it vehicular mobileterminal or normal mobile terminal) shall be improved.

In order to discuss these aspects, the following exemplary assumptionsare made. A vehicular mobile terminal is assumed which has been set upappropriately for performing direct communications with other mobileterminals, i.e., via corresponding sidelink connection(s). It is furtherassumed that the vehicular mobile terminal wants to communicate withother mobile terminal(s) and thus needs to determine particular sidelinkradio resources to be used in said respect.

According to a first aspect, the determination of these radio resourcesis improved. In particular, the first aspect distinguishes between twodifferent radio resource determinations, one where the location of thevehicular mobile terminal is considered and the other one where thelocation of the vehicular mobile terminal is not considered. As knownfrom the background section, the usual sidelink resource allocation(e.g., Mode 1 and Mode 2) does not consider the location of the(vehicular) mobile terminal, e.g., the mobile terminal autonomouslyselects radio resources from a radio resource pool (i.e., Mode 2) andthe radio base station decides on the radio resources without referenceto the location of the mobile terminal.

On the other hand, according to the first aspect, the resourceallocation for vehicular communication shall be improved by taking thelocation of the vehicular mobile terminal into account. This can forinstance be implemented such that radio resources that would be normallyavailable to the vehicular mobile terminal would be “restricted” basedon the location of the vehicular mobile terminal.

Exemplarily assuming the UE-autonomous resource selection (Mode 2),different radio resource pools could be defined for different possiblepositions of a vehicle, such that the vehicular mobile terminal willselect radio resources from that radio resource pool that is associatedwith the particular location of the vehicular mobile terminal. Thevehicular mobile terminal is configured with these different radioresource pools such that it can autonomously select among the variousradio resource pools based on its determined location. There are severalways on how the vehicular mobile terminal can be configured with thesedifferent radio resource pools. According to one way, explicitinformation on the radio resource pools (such as the radio resources andthe association with the possible locations of the vehicular mobileterminals) could be provided to the vehicular mobile terminal, e.g.,within the system information broadcast by the radio base station in itscell or within a message which is dedicated to the vehicular mobileterminal. In another implementation, the different radio resource poolsmay not be explicitly notified to the vehicular mobile terminal, but maybe determined by the vehicular mobile terminal itself based on generalinformation on available radio resources and on a set of rules allowingthe vehicular mobile terminal to assign on its own the available radioresources to the respective possible locations of vehicular mobileterminals thereby defining the different radio resource pools from whichthe vehicular mobile terminal can then select the necessary radioresources.

On the other hand, when exemplarily assuming the eNB-scheduled resourceallocation (i.e., Mode 1), then the vehicular mobile terminal willdetermine its location and provide information thereon in one form oranother to the radio base station, which in turn can then selectappropriate radio resources (for example, but not necessarily, from aradio resource pool) based on the received location information of thevehicular mobile terminal. For instance, the radio base station couldselect the radio resources such that other (vehicular) mobile terminalsin the vicinity will not experience interference from the vehicularmobile terminal communication. Correspondingly, the radio base stationwould then inform the vehicular mobile terminal on the decided radioresources, such that the vehicular mobile terminal may use them forcommunication with other mobile terminal(s).

In general, the location-assisted resource allocation shall assist inallocating radio resources that are orthogonal to each other, so as toreduce or completely avoid interference between nearby vehicular mobileterminals when they communicate at the same time.

However, this improved resource allocation may not be optimal in allsituations and thus shall be used selectively according to the firstaspect. In more detail, some entity in the communication system (e.g.,the eNB, or a ProSe-related entity, or an MME) may have control overwhether the improved location-assisted resource allocation is to be usedor the usual resource allocation without considering the location of thevehicular mobile terminal. This entity may take the decision based onvarious different parameters, such as the number of vehicles in therespective area, the speed of the vehicles, the cell topology of therespective area (e.g., highway or city center or rural, etc.) andpossibly other information. For instance, in case of a dense, andslow-moving, traffic situation, the entity may decide to not assist theresource allocation with the vehicle location. For example, it may bedifficult to distinguish the various locations of nearby vehicularmobile terminals, such that assistant the resource allocation withvehicle locations might not be helpful. On the other hand, in case offree-flowing, possibly middle or high-speed traffic, the entity maydecide that it is advantageous to also consider the vehicle locationwhen determining the radio resources for communication with other mobileterminals. On the other hand, it may also be possible to decide theother way rounds, considering that in a dense traffic situation, thehigh vehicle density (more UEs in the same location area than infreeways) pushes up the demand for resources Furthermore, whether to usethe location-assisted resource allocation or without location-assistancemay also depend on the time, for instance peak hours where the trafficis usually dense while at other times the traffic situation isdifferent.

Moreover, a vehicular mobile terminal shall somehow be able to determinewhich resource allocation (i.e., location-assisted or withoutconsidering its location) it is supposed to use at a particular point intime. Consequently, corresponding information must be provided to thevehicular mobile terminal, which may be done in various different forms,two examples of which will be briefly discussed below. According to onepossible implementation, the vehicular mobile terminal is provided withexplicit information on the result of the decision, e.g., by a flagbroadcast by the radio base station in its system informationinstructing the vehicular mobile terminal to use the vehicle location ornot. Another possible implementation allows the vehicular mobileterminal to deduce whether to consider its location from configuredparameters in the vehicular mobile terminal, e.g., from parameters thatare related to this improved location-assisted resource allocation andare used by the vehicular mobile terminal when determining its locationor when determining the radio resources.

So far, the first aspect was described in general terms regarding thelocation of the vehicular mobile terminal. However, there are differentways on how the location of the vehicular mobile terminal can bedetermined and presented. One possible way is to use the geographicalcoordinates, such as longitude and latitude, e.g., commonly known fromGPS. According to an improvement of the first aspect, the location of avehicle mobile terminal is determined as a section and/or subsection ofa road on which the vehicular mobile terminal is currently traveling on.So, in this sense each road has a corresponding identification, e.g., aroad or street name and/or number and a corresponding start and endlocation. Also, it is assumed that information on maps is available tothe vehicular UE, which may also contain information on the edges of theparticular road. In particular, roads are divided in sections and/orsubsections thus allowing the location of the vehicular mobile terminalto actually be simply represented by an identification of the sectionand/or subsection of the road instead of using geographical coordinates.Correspondingly, the vehicular mobile terminal will determine itslocation as a section of the road (which might still require thevehicular mobile terminal to first determine the geographicalcoordinates and then to “translate” these geographical coordinates intothe possible section/subsection of the road in which it is located).This would also be advantageous in those cases where the information ofthe determine position of the vehicular mobile terminal is to betransmitted to the radio base station (e.g., for Mode 1 resourceallocation, where the radio base station decides on the radioresources), since the amount of information that needs to be transmittedcan be thus reduced.

An exemplary division of the road is based on a grid overlaying a road,the grid thus defining sections, which in turn are further subdividedinto subsections. For example, each section may cover all lanes of theroad and may span a particular length of the road. This section is thendivided into a plurality of subsections, where, e.g., one subsection mayonly cover one or more, but not all, lanes of the road. The subsectionsmay span the same length of the road as the section, or may span only afraction of the section while the rest of the length of the section is“covered” by other subsection(s). Furthermore, within a particular areawith same or similar characteristics, each section shall be set up(i.e., divided) into the same plurality of subsections, such that thegrid is repeated from section to section along the road.

This division of a road in sections and subsections may repeat for everysection the same association between a location within the section(i.e., a subsection as a possible location of a vehicle) and particularradio resources available to vehicular mobile terminals located in thatsubsection. Within each section, the distribution of the available radioresources between the plurality of subsections of the section is suchthat interference shall be mitigated or avoided. For instance, thevarious radio resources associated to the subsections within a sectionshall be orthogonal to each other. Furthermore, since the sections, andthus the subsections and their associated (orthogonal) radio resources,repeat themselves, the interference caused by vehicular mobile terminalscommunicating in neighboring sections should be mitigated or avoided aswell.

According to a further improvement of the first aspect, the resourceallocation is further improved by implementing a sensing capability inthe vehicular mobile terminal, so as to determine whether potentialradio resources are or will be used by another mobile terminal, in whichcase these potential radio resources would be blocked and should not beused if possible. In particular, exemplarily assuming the UE-autonomousradio resource selection (Mode 2), the vehicular mobile terminal, beforeactually selecting radio resources from a radio resource pool which isassociated with its location, will determine whether these potentialradio resources (i.e., in the process of being selected by the vehicularmobile terminal) are actually already in use by another mobile terminal.For instance, the vehicular mobile terminal will be able to determinethis by, e.g., using RSSI (Received Signal Strength Indication)measurements wherein it measures the total received signal strength(which is a measure of the energy transmitted) on the correspondingResource Elements (REs) of a candidate (time-frequency) resources, e.g.,PRB pair. When the RSSI is greater than a certain threshold, it deducesthat said resources are occupied. It may in addition statisticallydeduce that the said resources will remain “busy” for a certain time(e.g., number of TTIs). This statistical deduction can be based on theUE implementation of the past “busy-ness” of the resources in the sameor neighboring pool or can be signaled by the network, e.g., in the RRCsignaling (Broadcast or Dedicated). For instance, a “busy-ness” of 2would mean that on average, the resources remain “busy”, after theobservation instance, for 2 control/ data cycles.

According to an alternative or additional method, individual candidateSA messages (PSCCH) would be received and decoded and the vehicularmobile terminal can check if these indicate any future “busy-ness” incoming control/ Data cycles. If an individual candidate SA is not beingtransmitted currently, the vehicular UE could assume the control (SA)and the corresponding Data resources as “free”. The “busy-ness” in SAmessage may also indicate a corresponding period of busy-ness duringwhich it intends to keep transmitting on the corresponding control/ Dataresources. In the simplest form it will be a Boolean value indicating“busy-ness” period as 1 cycle or some other ‘fixed’ number of Cycles.

Then, in such a case where the potentially to be selected radioresources are being blocked by another mobile terminal, the vehicularmobile terminal shall select different radio resources.

Furthermore, in case no other resources can be selected from the radioresource pool associated with the location of the vehicular mobileterminal (e.g., due to blocking as just explained), the vehicular mobileterminal shall be able to select radio resources from another radioresource pool, i.e., a radio resource pool associated with a locationwhich is not the location of the vehicular mobile terminal. For example,this other radio resource pool can be associated with a location whichis right next to the actual location of the vehicular mobile terminal;alternatively, the other radio resource pool can be associated with alocation which is further or even furthest away from the actual locationof the vehicular mobile terminal. Alternatively, or in addition,different relative priorities can be given to the various subsectionsand the associated radio resources based on the distance of thesubsection from the subsection in which the vehicular mobile terminal islocated. For instance, the priority decreases with increasing distance,such that a vehicular mobile terminal shall select radio resources fromanother radio resource pool associated with a subsection having thehighest (remaining) priority (i.e., a subsection right next to thesubsection in which the mobile terminal is located).

This additional improvement where a vehicular mobile terminal performs asensing of the potential radio resources prior to actually using them isespecially advantageous in scenarios where such radio resourcecollisions are likely to happen. For instance, it was discussed beforethat a road can be divided into sections and/or subsections, eachsubsection being associated with a particular set of resources (e.g., aresource pool) from which the vehicular mobile terminal (located in theassociated position) can select suitable radio resources. Depending onhow the sections and/or subsections are actually set up, a subsectionmay cover an area in which only one, or more than one, vehicular mobileterminals can be located at the same time and may thus use the sameassociated radio resources. The sensing as explained above for theimproved implementation of the first aspect can avoid such radioresource collisions by first determining whether radio resources arealready blocked before actually using these radio resources forcommunication with another mobile terminal.

According to a second aspect, which is different from the abovediscussed first aspect, the determination of the radio resources by avehicular mobile terminal is improved as well. Also the second aspectdistinguishes between two different radio resource determinations, inthis case however, one radio resource allocation comprises theadditional process of sensing whether radio resources are or will be inuse by another mobile terminal, while the other radio resourceallocation does not involve the additional sensing procedure.

Sensing has been already discussed above as a further improvement to thelocation-assisted radio resource determination of the first aspect, butis considered as a stand-alone improvement according to the secondaspect. As explained before, sensing shall be understood as a capabilityof the vehicular mobile terminal to determine whether potential radioresources are or will be used by another mobile terminal. In case thesepotential radio resources would be blocked by another (vehicular) mobileterminal, the vehicular mobile terminal may decide to not use them so asto avoid a collision, and rather proceed to determine different radioresources.

Sensing may involve at least two different ways on how to determinewhether radio resources are blocked or not. According to a first way,the received signal strength on corresponding radio resources (e.g.,resource elements of a candidate PRB pair) is measured by the vehicularmobile terminal and compared to a threshold, so as to finally considerthat the radio resource is blocked in case that the received signalstrength is larger than the threshold. Therefore, the vehicular mobileterminal is able to determine whether at this particular momentpotential radio resources are being used by another mobile terminal ornot.

In addition or as an alternative, the vehicular mobile terminal maymonitor SA (Scheduling assignment) messages transmitted by other mobileterminals as part of the D2D transmission procedure. The SA messageswill indicate the particular radio resources that will be used totransmit the associated data message (in the same or a later subframe).Consequently, the vehicular mobile terminal will thus be able to learnfrom the SA messages which radio resources will be likely used in thefuture by these mobile terminals, and thus be blocked from use.

Sensing can be performed by the vehicular mobile terminal whendetermining radio resources according to Mode 1 (eNB-scheduled) or Mode2 (UE-autonomous). In particular, assuming the UE-autonomous resourceallocation of Mode 2, the vehicular mobile terminal shall performsensing before actually using radio resources from a suitable radioresource pool. For instance, the vehicular mobile terminal might firstselect a potential set of resources from the radio resource pool, andmay then sense whether these selected resources are blocked by anothermobile terminal or not, and then repeat this procedure until thevehicular mobile terminal finds radio resources in the radio resourcepool that are free, i.e., not blocked by another mobile terminal. On theother hand, before even selecting a potential set of resources, thevehicular mobile terminal may perform the sensing on all possible radioresources of the radio resource pool, and will then disregard thoseradio resources from the radio resource pool that are blocked.Subsequently, the vehicular mobile terminal may select radio resourcesamong those free radio resources remaining in the radio resource pool.

As a further improvement to the second aspect, the radio resourceallocation can be improved by additionally considering the location ofthe vehicular mobile terminal as explained in detail for the firstaspect. In order to avoid repetition, reference is made to the abovepassages of the first aspect discussing how the vehicular mobileterminal determines its location and considers same when determining theradio resources, how the location of the vehicular mobile terminal canbe used in Mode 1 as well as Mode 2 radio resource allocation, how thelocation can be geographical coordinates or identifiers indicatingsections and/or subsections into which a road is divided, etc.

Correspondingly, in one general first aspect, the techniques disclosedhere feature a vehicular mobile terminal for determining radio resourcesfor communicating with at least a second mobile terminal in acommunication system. A processor of the vehicular mobile terminaldetermines whether to determine radio resources based on the location ofthe vehicular mobile terminal or not, wherein the determination is basedon information received from an entity of the communication system. Incase the radio resources are to be selected based on the location of thevehicular mobile terminal, the processor determines the location of thevehicular mobile terminal, and determines radio resources forcommunication with at least the second mobile terminal, based on thedetermined location of the vehicular mobile terminal.

Correspondingly, in one general first aspect, the techniques disclosedhere feature a radio base station in a communication system forassisting a vehicular mobile terminal in determining radio resources forcommunicating with at least a second mobile terminal in thecommunication system. A processor of the radio base station determineswhether radio resources are to be determined based on the location ofthe vehicular mobile terminal or not. The determination is at leastbased on information on vehicular mobile terminals in the cell of theradio base station. A transmitter of the radio base station transmitsinformation to the vehicular mobile terminal, based on which thevehicular mobile terminal determines whether to determine radioresources based on the location of the vehicular mobile terminal or not.

Additional benefits and advantages of the disclosed embodiments will beapparent from the specification and Figures. The benefits and/oradvantages may be individually provided by the various embodiments andfeatures of the specification and drawings disclosure, and need not allbe provided in order to obtain one or more of the same.

These general and specific aspects may be implemented using a system, amethod, and a computer program, and any combination of systems, methods,and computer programs.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

In the following exemplary embodiments are described in more detail withreference to the attached figures and drawings.

FIG. 1 shows an exemplary architecture of a 3GPP LTE system,

FIG. 2 shows an exemplary downlink resource grid of a downlink slot of asubframe as defined for 3GPP LTE (Release 8/9),

FIG. 3 schematically illustrates how to establish a layer-2 link overthe PC5 for ProSe communication,

FIG. 4 illustrates the use of transmission/reception resources foroverlay (LTE) and underlay (D2D) systems,

FIG. 5 illustrates the transmission of the Scheduling Assignment and theD2D data for two UEs,

FIG. 6 illustrates the D2D communication timing for the UE-autonomousscheduling Mode 2,

FIG. 7 illustrates the D2D communication timing for the eNB-scheduledscheduling Mode 1,

FIG. 8 illustrates an exemplary architecture model for ProSe for anon-roaming scenario,

FIGS. 9A, B, C exemplarily illustrate different divisions of a road intosubsections and sections according to the embodiments, and

FIG. 10 illustrates exemplarily a sequence diagram for an operation ofthe vehicular UE according to the first embodiment.

DETAILED DESCRIPTION

A mobile station or mobile node or user terminal or user equipment is aphysical entity within a communication network. One node may haveseveral functional entities. A functional entity refers to a software orhardware module that implements and/or offers a predetermined set offunctions to other functional entities of a node or the network. Nodesmay have one or more interfaces that attach the node to a communicationfacility or medium over which nodes can communicate. Similarly, anetwork entity may have a logical interface attaching the functionalentity to a communication facility or medium over which it maycommunicate with other functional entities or correspondent nodes.

The term “radio resources” as used in the set of claims and in theapplication is to be broadly understood as referring to physical radioresources, such as time-frequency resources.

The term “direct communication transmission” as used in the applicationis to be broadly understood as a transmission directly between two userequipments, i.e., not via the radio base station (e.g., eNB).Correspondingly, the direct communication transmission is performed overa “direct sidelink connection”, which is the term used for a connectionestablished directly between two user equipments. For example, in 3GPPthe terminology of D2D (Device-to-Device) communication is used or ProSecommunication, or a sidelink communication. The term “direct sidelinkconnection” is to be broadly understood and can be understood in the3GPP context as the PC5 interface described in the background section.

The term “ProSe” or in its unabbreviated form, “Proximity Services”,used in the application is applied in the context of Proximity-basedapplications and services in the LTE system as exemplarily explained inthe background section. Other terminology such as “D2D” is also used inthis context to refer to the Device-to-Device communication for theProximity Services.

The term “vehicular mobile terminal” as used throughout the applicationis to be understood in the context of the new 3GPP study item V2X(vehicular communication) as explained in the background section.Correspondingly, a vehicular mobile terminal shall be broadly understoodas a mobile terminal which is specifically installed in a vehicle (e.g.,car, commercial trucks, motorcycles etc.) to perform vehicularcommunication, i.e., passing information related to the vehicle to otherentities (such as vehicles, infrastructure, pedestrians), e.g., for thepurpose of safety or driver assistance. Optionally, the vehicular mobileterminal may have access to information available at the navigationsystem (provided it is also installed in the car), such as mapinformation, etc.

The term “road” as used throughout the application is to be broadlyunderstood as covering any piece of land on which a vehicle can bedriven, including highways, motorways, paths, routes, streets, avenues.

As explained in the background section, 3GPP has introduced a new studyitem for LTE-assisted vehicular communication, which shall be based onProSe procedures including the resource allocation according to Mode 1and Mode 2. However, the resource allocation based on ProSe may not besufficient to fulfill all the requirements for V2X communication andmight thus need to be adapted.

The following exemplary embodiments are conceived by the inventors tomitigate one or more of the problems explained above.

Particular implementations of the various embodiments are to beimplemented in the wide specification as given by the 3GPP standards andexplained partly in the background section, with the particular keyfeatures being added as explained in the following pertaining to thevarious embodiments. It should be noted that the embodiments may beadvantageously used for example in a mobile communication system, suchas 3GPP LTE-A (Release 10/11/12/13) communication systems as describedin the Technical Background section above (or later releases), but theembodiments are not limited to its use in this particular exemplarycommunication networks.

The explanations should not be understood as limiting the scope of thedisclosure, but as a mere example of embodiments to better understandthe present disclosure. A skilled person should be aware that thegeneral principles of the present disclosure as laid out in the claimscan be applied to different scenarios and in ways that are notexplicitly described herein. For illustration purposes, severalassumptions are made which however shall not restrict the scope of thefollowing embodiments.

Furthermore, as mentioned above, the following embodiments may beimplemented in the 3GPP LTE-A (Rel. 12/13) environment, but possiblyalso in future releases. The various embodiments mainly provide animproved resource allocation for vehicular mobile terminals. Therefore,other functionality (i.e., functionality not changed by the variousembodiments) may remain exactly the same as explained in the backgroundsection or may be changed without any consequences to the variousembodiments. This includes, e.g., other procedures relating to theactual use of the determined (sidelink) radio resources i.e., after theradio resources have been selected, and the vehicular UE uses them toperform the transmission of data (possibly including the transmission ofthe scheduling assignment too).

First Embodiment

In the following a first embodiment for solving the above-mentionedproblem(s) will be described in detail. Different implementations andvariants of the first embodiment will be explained as well.

Exemplarily, a vehicular UE is assumed which is installed in a vehicleand is capable of performing vehicular communication based on the D2Dframework as explained in the background section of this application. Itis further assumed that the vehicular UE shall communicate with otherUEs and thus needs to first determine suitable sidelink radio resourcesto be used for said purpose. The first embodiment focuses on how thesidelink radio resources can be efficiently determined by the vehicularUE so as to then be able to communicate with other (vehicular) UEs in ausual manner using these determined radio resources.

The radio resource allocation according to the first embodiment is basedon the radio resource allocation as already defined for D2Dcommunication, thus generally distinguishing between Mode 1 and Mode 2resource allocations as explained in detail in the background section.Independently from the Mode 1 and Mode 2 resource allocations however,the first embodiment additionally distinguishes between two differentradio resource allocations, which differ from one another as will beexplained in the following. One of the two radio resource allocationsshall be the common radio resource allocation as explained in detail inthe background section for D2D communication; as apparent therefrom, thelocation of the (vehicular) UE has no influence on which radio resourcesare determined in the Mode 1 or Mode 2 resource allocation procedure. Onthe other hand, the second radio resource allocation according to thefirst embodiment is based on the radio resource allocation for D2Dcommunication too but additionally considers the location of thevehicular UE when determining the radio resources as will be explainedin more detail below.

The vehicular UE shall determine the radio resources according to one ofthe two above-mentioned radio resource methods and thus must beinformed/instructed which resource allocation it shall use. This step ofinforming the vehicular UE on which method of resource allocation to usemay be performed by a suitable entity in the mobile communication systemsuch as the eNodeB, an MME or a ProSe-related entity in the corenetwork. This entity may also be responsible for deciding which resourceallocation method to use and also responsible for letting the UE knowwhich resource allocation method it shall use. For ease of explanation,in the following it is exemplarily assumed that it is the eNodeB whichis the entity responsible for taking the decision and informing thevehicular UEs.

Assuming that the vehicular UE is to use the improved resourceallocation method introduced by this first embodiment, the vehicular UEshall determine its location and then determine radio resources on thebasis of the just determined location of the vehicular UE.

On the other hand, assuming that the vehicular UE is not to use theimproved location-assisted resource allocation method but the usualresource allocation method as explained before for D2D, then it is notnecessary for the vehicular UE to determine its location for the radioresource determination. Rather, the vehicular UE will determine suitableradio resources for communication with another UE according to Mode 1 orMode 2 in the usual manner.

As broadly presented above, the improved location-assisted resourceallocation method introduced with this first embodiment shall beselectively used under control of an entity in the mobile communicationsystem such as the eNodeB. Correspondingly, the resource allocation thatalso considers the vehicle location is not applied in all situations butcould only be applied when providing substantial benefits.

In general, it should be noted that additionally considering thelocation of vehicular UEs in the resource allocation process can havethe following benefits. Using location as a basis for resourceallocation allows the network to dedicate different amount of resourcesfor V2X communication based on traffic statistics, e.g., higherresources for V2X communication in more traffic-dense location and lowerresources for V2X communication in sparse traffic areas. Furthermore,for special implementations of the first embodiment to be discussedlater, location and having corresponding resources requires thevehicular UE to sense only a limited portion of the available resourcepool. For example, if there are up to 32 resource pools configured andonly couple of them belongs to the vehicular UE’s location, then it onlyneeds to perform sensing in these two resource pools. This not onlysaves time but also battery.

On the other hand, determining the location of the vehicular UE, andalso possibly transmitting information thereon to the eNB for radioresource allocation has the disadvantage of requiring the vehicular UEsto repeatedly track its location and of spending radio resources forinforming the eNB on this location so as to assist in the resourceallocation. The benefits and disadvantages provided by thelocation-assisted resource allocation need to be balanced. Consequently,the first embodiment selectively uses the improved location-assistedresource allocation method for particular situations but not for others.

FIG. 10 is a sequence diagram for a vehicular UE exemplarily illustratesthe operation of the vehicular UE as explained above for the firstembodiment.

In the following more specific implementations of the first embodimentwill be explained which may provide further advantages.

The above broad explanation of the first embodiment involves an entity(e.g., the eNB) which selectively decides as to whether to use oneresource allocation method or the other; i.e., to additionally considerthe vehicular UE location or not. As explained above, additionallyconsidering the vehicle location for the resource allocation can providebenefits especially in particular scenarios. Correspondingly, the eNBcan base its decision on suitable information that allows to distinguishbetween these different situations. This information may for instanceinclude at least one of the following: information on the number ofvehicles in a particular area, the speed and/or direction of thevehicles, the traffic situation in the particular area (e.g., whetherthere is dense traffic or free-flowing traffic, traffic jam), the celltopology of the particular area (e.g., highway, city center, or rural),the time of day since traffic situations may change during the day. Forparticular implementations of the first embodiment, other informationwhich may be important for this decision may include information on howthe road is divided into sections and/or subsections as will beexplained in detail later. Correspondingly, the eNB may also considerthe particular division of the road into subsections and sections whenmaking the decision as to whether particular vehicular UEs shall use ornot its vehicle location when determining the radio resources.

The following two examples are provided in order to understand how sucha decision can be performed. For instance, a dense and slow movingtraffic situation is assumed where vehicles are located side-by-sidesuch that it may be difficult to distinguish between the variouslocations of these nearby vehicular UEs. In said case, the benefit thatcan be gained from additionally using the location information for theresource allocation may become minimal, and thus the eNB may decide thatthe vehicular UEs in a particular area shall not use the improvedlocation-assisted resource allocation method but to use the usual D2Dresource allocation.

In another example, a free-flowing traffic situation is assumed wherethe vehicles may travel at mid or high speed and where it is easilypossible to distinguish the location of the various vehicles due to thedistance which is being kept in between by the vehicle drivers.Correspondingly, in such a situation it may be beneficial to assist theradio resource allocation by also considering the location of thevarious vehicles.

Consequently, the eNB will take such a decision in either way and shallthen ensure that the vehicular UE(s) are instructed to perform theresource allocation in accordance therewith.

Many ways can be envisaged on how the vehicular UE is provided withsuitable information on whether to use one resource allocation method orthe other. This also depends on the cell area controlled by the eNodeB.In particular, cell areas can be small or large and may thus also bedifferent in that they cover a particular homogenous area with similartraffic situations where the eNodeB will reach the same decision as towhether to use the location-assisted resource allocation or not. In saidcase, all vehicular UEs reachable by the eNodeB in its cell will beconfigured in the same manner to use or not use the location-assistedresource allocation and in general the eNodeB could provide thecorresponding information in a broadcast in its cell.

On the other hand, the cell of an eNodeB may cover several differentroads with different characteristics leading the eNodeB to distinguishbetween different areas of its cell as regards to whether to use thelocation-assisted resource allocation or not. Correspondingly, only someof the vehicular UEs reachable by the eNodeB in its cell will beconfigured in the same manner while others will be configureddifferently. In this case, a cell broadcast may not be applicable butthe different vehicular UEs could be configured/informed by dedicatedmessages.

According to one possible implementation of the first embodiment, thevehicular UE is explicitly instructed to perform either of the tworesource allocation methods, which can be done by a corresponding flagwhich in turn may be transmitted either in system information broadcastby the eNodeB in its cell or in a corresponding dedicated messageaddressed to particular vehicular UE(s) as just explained. The flag canbe one bit long where each of the two bit values unambiguously instructsthe vehicular UE to use either one of the two resource allocationmethods distinguished in the first embodiment.

Alternatively, or in addition, instead of providing an explicitinstruction to the vehicular UE, a second implementation of the firstembodiment is based on that the vehicular UE will deduce whether to usethe improved location-assisted resource allocation method or not fromits internal configuration. In particular, in order to apply thelocation-assisted resource allocation method, the vehicular UE(s) willusually be configured with additional parameters that are related tothis improved location-assisted resource allocation. For instance, aswill be explained in detail below, the location of the vehicular UE canbe determined on the basis of sections and/or subsections into which aroad is divided. In that case, in order for the vehicular UE to be ableto identify the particular sections and/or subsections, it may beprovided with suitable information on the sections and/or subsections ofroads. Therefore, if the vehicular UE is configured with such parametersfor use in determination of the location, it will determine that itshall also make use of these parameters and thus shall use thelocation-assisted resource allocation method. Conversely, if thevehicular UE notices that no such parameters have been configured sofar, it will determine that the improved location-assisted resourceallocation method shall not be used; actually, the vehicular UE wouldnot be able to determine the location as a function of thesections/subsections due to the missing parameters. This is however onlyan example, and also other parameters may be configured in the vehicularmobile terminal in connection with the two resource allocation methods.For instance, in case the normal D2D resource allocation method shall beused, an implementation of the first embodiment provides a particular,larger, radio resource pool specifically for the vehicularcommunication. In that case, if the vehicular UE determines that such alarger radio resource pool is configured, it will deduce to use thenormal D2D resource allocation method instead of the location-assistedresource allocation method. These radio resource pools may be signaledas in the legacy, e.g., common resource pool in SIB 19 or sending thededicated resource pool using RRC dedicated message to the RRC ConnectedUEs.

In any case, according to the various implementations of the firstembodiment, each of the vehicular UEs will know at any time whether touse one resource allocation method or the other.

The above broad explanation of the first embodiment generally explainedthat the vehicular UE will determine the radio resources based on itslocation, without going into detail as to how the radio resources areactually determined. As explained before, both radio resource allocationmethods distinguished by the first embodiment may exemplarily be basedon the common D2D resource allocation as explained in detail in thebackground section. Correspondingly, according to implementations of thefirst embodiment, Mode 1 and Mode 2 resource allocations aredifferentiated as well, respectively being extended so as to considerthe vehicular UE location as well.

According to the Mode 1 resource allocation, the eNB controls whichradio resources shall be used in its cell by the (vehicular) UEs.Correspondingly, the vehicular UEs, when radio resources need to bedetermined, will request the eNodeB (that controls the radio cell inwhich the vehicular UE is located) for such radio resources. In detail,this may be done by the vehicular UE transmitting a scheduling requestfollowed by a buffer status report to the eNodeB, as explainedexemplarily in the background section for the current 3GPP release forD2D communication.

The eNodeB learns that this particular vehicular UE has data totransmit, based on the received scheduling request and buffer statusreport and can then decide on the particular radio resources to bescheduled for this vehicular UE so as to allow it to communicate withother UEs. According to the improved location-assisted resourceallocation method of the first embodiment, the eNodeB will additionallyreceive location information from the vehicular UE (e.g., together withthe buffers status report and the scheduling request) and will also takeinto account this vehicular location information when determining theradio resources. In particular, the eNodeB will be aware of the locationof various vehicular UEs and normal UEs in its area and can thus makeuse of its knowledge of topology, vehicle density, traffic demands, outof band emissions, interference situation, etc., to schedule resourcesto nearby vehicular UEs such that interference between them ismitigated.

A corresponding response from the NodeB to the vehicular UE will theninclude a suitable indication of the radio resources the vehicular UEshall use for communication with other mobile terminal(s). The vehicularUE will receive the corresponding response from the eNodeB and can thenperform the vehicular communication, e.g., comprising the transmission,in the usual manner, of the scheduling assignment message and of thedata on the radio resources as scheduled by the eNodeB.

For the Mode 1 resource allocation method as just described, it isassumed that the eNodeB is provided with the vehicular UE location. Thismay be done in various manners and also depends on the actual content ofthe vehicular UE location that is transmitted to the eNodeB. As will beexplained later in more detail, the vehicular UE location may begenerally presented as geographical coordinates (e.g., GPS) or as asection/subsection into which roads can be divided. Correspondingly,there is also a difference as to the amount of data that is transmitted,where the geographical coordinates need more data and the IDs of asection/subsection presumably will need less data. In any case, thevehicular UE location may be transmitted to the eNodeB together with thescheduling request and the buffer status report. The information on thevehicular UE location may be carried separately from the schedulingrequest and the buffer status report, or the scheduling request might beextended with a field carrying said information on the vehicular UElocation. Another possible way to do it will be to use the RRCSidelinkUEInformation message including the latest location each timethe location information changes substantially like, e.g., every 100 ms.or so.

Correspondingly, the vehicular UE will be able to determine radioresources according to Mode 1 additionally based on its own location.This Mode 1 request will include SidelinkUEInformation message includingdetails of size and periodicity of required V2X/ V2V messagetransmission and subsequently the BSR reports indicating any changes inthe Buffer Occupancy, etc.

According to the Mode 2 resource allocation, also termed UE-autonomousresource selection, a UE is adapted to select the radio resources on itsown, e.g., from the available radio resource pools, in order to be ableto transmit the control information (SA message) and user data via adirect sidelink connection. As mentioned before, the first embodimentadditionally provides a resource allocation method which is able to takeinto account the location of the vehicular UE. This could be implementedexemplarily in the first embodiment by providing different radioresource pools for different possible locations of the vehicular UE. Inparticular, a plurality of radio resource pools would then have to beconfigured in the vehicular UE, each one of which would be associatedwith a different location in which a vehicular UE can be located.Correspondingly, at the time when the vehicular UE needs to determineradio resources, and after determining its own location, the vehicularUE will first determine which radio resource pool to use, namely thatone which is associated with the determined vehicular UE location, andthen will select appropriate radio resources from that associated radioresource pool for transmitting the scheduling assignment and the data.

The configuration of the plurality of radio resource pools in thevehicular UE(s) mentioned above may be under control of the eNodeB.Correspondingly, the eNodeB has to provide the vehicular UE(s) with thenecessary information on the plurality of radio resource pools and theirrespective association with potential vehicular UE locations. Accordingto one implementation of the first embodiment, the radio resource poolsmay be explicitly notified to the vehicular UEs, e.g., as a tableidentifying the radio resources and the associated location. Thefollowing exemplary table is presented in said respect, which assumesthat x different radio resource pools are defined. The parameter x ofcourse may vary depending on the size of the radio cell under control ofthe eNodeB, the available radio resources that the eNodeB intends tomake available to vehicular UEs in its radio cell, and possibly alsoother conditions including traffic types/ speed, etc.

TABLE 1 Location Radio Resource Pool Position 1 Offset1; Number of PRBs;PRB-Start; PRB-end Position 2 Offset2; Number of PRBs; PRB-Start;PRB-end Position 3 Offset3; Number of PRBs; PRB-Start; PRB-end ... ...Position x Offsetx; Number of PRBs; PRB-Start; PRB-end

Correspondingly, such a table may be provided by the eNodeB to thevarious vehicular UEs in its radio cell, e.g., as part of the systeminformation (if the eNodeB would like to configure all vehicular UEs inits cell in the same manner) or alternatively/additionally within amessage dedicated to particular vehicular UEs.

As a further improvement, it may be possible to transmit common values,such as the number of PRBs, only once instead of transmitting same foreach and every resource pool, thereby reducing the amount of data thatthe eNodeB has to transmit to the vehicular UE(s).

As an alternative to providing so much information about the radioresource pools from the eNodeB to the vehicular UE(s), alternativeimplementations of the first embodiment provide that the vehicular UEsthemselves shall be able to determine the radio resource pools and theassociated locations. This may be done by the use of a set of ruleswhich may divide a large pool of resources in several radio resourcepools associated with different locations. For instance, the vehicularUE may sequentially assign a fixed amount of radio resources from alarger pool of radio resources to particular locations, therebygenerating different radio resource pools for different locations. Thiscould look like a physical grid of resources where in the simplest formeach portion of grid represents a part from the whole available pool ofresources such that the adjoining portion of the grid represents thenext part from the whole available pool of resources and so on.

According to further implementations of the first embodiment, theresource allocation shall be further improved by providing the vehicularUE with a sensing capability of radio resources as will be explained inthe following. The exemplary term “sensing capability” shall be broadlyunderstood as the capability of a vehicular UE to determine whethercandidate radio resources (i.e., radio resources that may be used forthe vehicular communication) are or will be used by other (vehicular)UEs or not, in order to then, if possible, not use these “blocked” radioresources to avoid corresponding collisions with the other (vehicular)UEs. Rather, the vehicular UE shall use, if possible, other radioresources which are determined to not be already in use by another(vehicular) UE. This sensing capability can be applied by the vehicularUE for both Mode 1 and Mode 2 resource allocations and on top of theadditional consideration of the vehicle location when determining theradio resources as explained above in detail.

In general, sensing provides various benefits. For instance, a sensingbased collision avoidance mechanism helps reduce resource collision,e.g., when a UE reads other UE’s control information in order to avoidusing the same resource for its transmission. Furthermore, sensing basedresource allocation and location based resource pool partitioning havesignificant performance gain i.e., PRR (Packet Reception Ratio) goes upsignificantly for resource selection/ allocation method with Sensing.PRR basically describes what percentage of vehicles in a given range(e.g., 100 m.) receive the transmitted packet from the given VehicularUE. Also, sensing reduces the number of transmissions by a UE leading tolower in-band emissions. This leads to better near far performance andsaves resources.

It is exemplarily assumed that the vehicular UE is configured for Mode-2resource allocation and additionally considers the vehicle location forthe radio resource determination according to the first embodiment andthus the vehicular UE shall autonomously select radio resources from aradio resource pool which is associated with the determined location ofthe vehicle UE. In addition, the vehicular UE shall perform sensing soas to not use radio resources that are or will be used by another(vehicular) UE. This may be implemented in different ways. For instance,the vehicular UE will select a candidate set of radio resources from asuitable radio resource pool which is associated with its location.However before actually using the candidate set of radio resources, thevehicular UE shall first determine where these radio resources areactually blocked by another mobile terminal or not. Then, in case theradio resources are or will already be used by another mobile terminal,the vehicular UE shall repeat the process and select different radioresources from the radio resource pool, which are then again checked asto whether they are blocked or not. This process may be continued untilthe vehicular UE determines radio resources from the radio resource poolthat are not blocked by another mobile terminal. On the other hand, thevehicular UE, before actually selecting a candidate set of radioresources from the radio resource pool, may perform the sensing on allradio resources of the radio resource pool and then eliminate/disregardthose radio resources from the radio resource pool that have beendetermined to be or that will be in use by another UE. Correspondingly,the vehicular UE will then select radio resources from among theremaining free radio resources of the radio resource pool to be used forcommunication.

A further improvement of this sensing capability considers the situationthat all radio resources of a radio resource pool are or will be in useby another mobile terminal, such that the vehicular UE will be blockedfrom performing vehicular communication for a particular time. In orderto avoid this, an implementation of the first embodiment allows that thevehicular UE can select radio resources from another radio resourcepool, i.e., a radio resource pool which is actually not associated withits own location but with another location. This will increase thelikelihood that radio resources from this other radio resource pool willnot be blocked and will enable the vehicular UE to perform the vehicularcommunication using said radio resources. As mentioned above, thevehicular UE may be configured with a plurality of different radioresource pools and, according to one implementation, the UE mightrandomly determine another radio resource pool from which select theradio resources. Alternatively, instead of randomly selecting anotherradio resource pool, the vehicular UE may use a radio resource poolwhich is associated with a location which is right next to the actuallocation of the vehicular UE. On the other hand, the vehicular UE mayuse another resource pool which is associated with a location which isfurther, or even further away, from the actual location of the vehicularUE. According to still another alternative, the vehicular UE may assigna relative priority to each of the available radio resource pools basedon a previously determined priority assignment scheme. Then, thevehicular UE may select that radio resource pool from the remainingradio resource pools with the highest priority. For example, relativepriorities may be assigned to the plurality of radio resource poolsbased on the distance from the actual location of the vehicular UE, suchthat radio resource pools associated with a nearby or further awaylocation will be assigned a high priority.

On the other hand, when assuming Mode 1 resource allocation, thevehicular UE, after having received from the eNodeB a message indicatingradio resources that shall be used by the vehicular UE forcommunication, shall also perform sensing on these received andinstructed radio resources before actually using them for thecommunication. In the same manner, the vehicular UE may reach theconclusion that the instructed radio resources are or will be used byanother (vehicular) UE and will thus not use them in order to avoid thecollision. Rather, the vehicular UE may then again request resourcesfrom the eNodeB, or may proceed to autonomously select radio resourcesfrom a suitable radio resource pool (e.g., associated with its location)in order to avoid the delay incurred by again having to request radioresources from the eNodeB.

The vehicular UE can determine that radio resources are or will be inuse in at least two different ways. According to a first implementation,the vehicular UE will measure the received signal strength (e.g., RSSI,received signal strength indication) on corresponding resource elements(REs) of candidate resources, e.g., PRBs. The received signal strengthis an indication on whether these radio resources are already in use byanother mobile terminal. Correspondingly, by comparing the measuredreceived signal strength against a suitable threshold, the vehicular UEmay identify radio resources that must be considered to be already inuse by another UE and thus blocked for the vehicular UE. Furthermore,the vehicular UE may continue measuring the received signal strength forthe candidate resources and thus determine when the other UE will stopusing them, or will simply assume that these radio resources are blockedfor a particular period of time (e.g., determined statistically frompreviously monitoring the radio resources or as being instructed by thenetwork via corresponding RRC signaling) without having to actuallycontinue measuring the received signal strength for those radioresources.

According to the second implementation, the vehicular UE may monitorscheduling assignment messages transmitted by other (vehicular) UEs,which indicate which radio resources will be used for transmitting thedata. Correspondingly, the vehicular UE will thus learn which radioresources will be used by other mobile terminals. Furthermore, the SAmessages may also indicate a period during which the radio resourceswill be repeatedly used, thus allowing the vehicular UE to determineblocked radio resources in the future.

These two different implementations on how the vehicular UE candetermine whether radio resources are blocked or not, can be used inparallel or separately from one another, or only one of them may be usedby the vehicular UE.

In general, additionally including the process of sensing by thevehicular UE before actually using radio resources is especiallyadvantageous in those scenarios where radio resource collisions arelikely to happen. Although not discussed so far, depending on howprecise the possible vehicle locations are differentiated from oneanother, at a particular location there may be only one vehicular UE orsubstantially more than one vehicular UE. For instance, it is assumedthat a radio resource pool is associated with a particular location(area) in which several vehicular UEs could be located at the same time,such that the several vehicular UEs could at the same or similar timeselect radio resources from this radio resource pool thereby increasingthe likelihood of selecting the same radio resources and thus causing acollision. By implementing this sensing capability in the vehicular UEs,some of these collisions will be avoided thereby increasing thethroughput in the vehicular communication and avoiding retransmissions.

According to the previously explained broad embodiment, it was assumedthat the vehicular UE determines its location and use the same fordetermining the radio resources (either using Mode 1 or Mode 2 radioresource allocation). As will be explained in the following, someimplementations of the first embodiment focus on how the location of thevehicular UE can be represented in an efficient manner.

According to one possible way, the vehicular UE location may beexpressed as geographical coordinates, which can be derived in a knownmanner, e.g., based on GPS satellites. The geographical coordinateswould at least include values for the longitude and latitude, e.g., indecimal degrees or in degrees, minutes, and seconds. In this case, thevehicular UE will determine its geographical coordinates and will thentake these geographical coordinates into account when determining thenecessary radio resources. For instance, for Mode 1 resource allocation,the vehicular UE will transmit these geographical coordinates to theeNodeB, which in turn would use them for selecting appropriate radioresources, and for sending a corresponding message with the scheduledradio resources back to the vehicular UE. For Mode 2 resourceallocation, the UE would compare its determined location with thegeographical coordinates associated with the different radio resourcepools and might then select that radio resource pool which is associatedwith geographical coordinates nearest to the ones of the vehicle.

According to another implementation of the first embodiment, thevehicular location will be represented completely different, namely as afunction of sections and/or subsections into which a road is divided.This will be explained with reference to FIGS. 9A, 9B, and 9C whichillustrate exemplary divisions of a road into sections and subsections.Each of these figures is exemplarily based on a 4-lane road, where all 4lanes are supposed to carry traffic going in the same direction. Asillustrated in these figures, there are many possibilities on how a partof the road can be divided into different sections and subsections. ForFIGS. 9A, 9B and 9C it is exemplarily assumed that each section coversall of the lanes of the road, although this does not need to be thecase. Furthermore, the same stretch of a road can be divided into adifferent number of sections, where the different sections then woulddiffer in their length. In turn, also the subdivision of these sectionsinto subsections can be performed in many different ways. For instance,in FIGS. 9A and 9B it is exemplarily assumed that 16 differentsubsections are provided as illustrated. On the other hand, according toFIG. 9C, the subsections are supposed to cover only one lane but are thesame length as the section thus resulting in fewer subsections.

How the sections and the subsections are set up may be decided by asuitable entity in the mobile communication system, such as the one thatis also responsible to decide which radio resource allocation method touse (e.g., the eNodeB, the MME, or a ProSe related entity). The lengthand breadth of the sections and subsections may be decided by thisentity, which may consider different parameters in said respect. In theexemplarily assumed scenarios of FIGS. 9A, 9B and 9C, the breadth of thesection is equal to the breadth of the road, while the breadth of asubsection is equal to the breadth of a lane (e.g., 4 m). The length ofa subsection may depend on the speed of the vehicles that are travelingon that road, the resulting inter-vehicle distance as a function of thevehicle speed, and also on whether only one car shall be assumed persubsection or several cars per subsection. For example, in case thereshould be only one car per subsection, an inter-vehicle distance in thesame lane of about 97 m (2.5 seconds * 140 km/h, see Table A.1.2-1 of TS36.885 for the highway scenario) could be used as the length of asubsection to ensure that only one vehicle is located in the samesubsection. These are the example data for absolute vehicle speed in thefreeway case. The freeway case has been selected since it represents thefastest moving traffic scenario and apparently the time to react (forthe vehicle drivers for instance) is minimum in this case. So, if thefastest required latency can be met in freeway case to send criticalmessages across to other vehicles in freeways case, it might likely bepossible in other cases as well.

On the other hand, the length of the section may be determined based onthe required effective range of the vehicular communication as given inTable A.1 of TS 22.885. For instance, for the highway (Autobahn) case,the required effective range is 320 meters. Furthermore, in order tomake sure that interference is mitigated between two adjoining sections,it is exemplarily assumed that twice the required effective range shallbe used as the length of the section, i.e., 640 meters. In such a case,assuming the length of a section with 640 meters and assuming the lengthof a subsection to be about 97 meters, an exemplarily division maydivide the length of a section into seven subsections each with a lengthof 91 meters.

Alternatively, it is also feasible to provide longer subsections in viewof that the UE is supposed to make only one transmission in, e.g., 100ms, such that it may not be efficient to occupy the whole resources of asubsection for the UE also for the remaining 99 ms. In said case, byincreasing the length of the subsections it is possible to have morethan one vehicular UE in a subsection. This is exemplarily illustratedin FIG. 9C, which has subsections having the same length as the section.Correspondingly, when exemplarily assuming Mode 2 resource allocation, asubsection would still be associated with a radio resource pool, and thevehicular UEs located in that subsection will randomly select radioresources from the same radio resource pool associated with thatsubsection to perform vehicular communication. This is also a scenariowhere it is particularly advantageous to also apply the additionalsensing described above since several UEs are selecting radio resourcesfrom the same radio resource pool and may thus cause a collision; whichcan be avoided by having the vehicular UEs first determine whether radioresources are or will be free before actually using them.

As exemplarily explained above, a road may thus be divided into sectionsand subsections of particular length and breadth. Furthermore, it isassumed that each section, at least for a particular area, should bedivided in the same manner into subsections, as illustrated in therespective FIGS. 9A, 9B, and 9C. Put differently, a road is thus dividedinto various subsequent sections that are in turn subdivided in the samemanner into subsections.

Each of the subsections may then be associated with (different) radioresources, such that the radio resources of a particular vehicular UEcan be determined by taking also the location of the vehicular UE (i.e.,the section/subsection) into account. For example, when assuming Mode 2resource allocation, each subsection could be associated with adifferent radio resource pool. An exemplary association is illustratedin the following table, which is similar to the previously-discussedtable where the radio resource pools are more generally associated withthe vehicle locations.

TABLE 2 Location Radio Resource Pool Subsection 1 Offset1; Number ofPRBs; PRB-Start; PRB-end Subsection 2 Offset2; Number of PRBs;PRB-Start; PRB-end Subsection 3 Offset3; Number of PRBs; PRB-Start;PRB-end ... ... Subsection x Offsetx; Number of PRBs; PRB-Start; PRB-end

As apparent from the above table, it suffices for the vehicular UE todetermine the subsection it is in, considering that each section isdivided in the same manner into subsections which are then equallyassociated with the same radio resource pools. Thus, although thevehicular UE could also use the section (e.g., to possibly furtherdifferentiate between different radio resource pools), this is actuallynot necessary with the above assumptions.

The radio resources in the plurality of radio resource pools to bedistributed among the subsections of each section may be selected suchthat interference between them is mitigated. Correspondingly, vehicularUEs located in adjoining subsections and thus using the respectiveresources associated to that subsections should not cause interferencewhen communicating at the same time.

Based on the above described grid of sections and subsections which isoverlaid over each road, the vehicular UEs have to determine in whichsection/subsection they are in so as to then either use this informationon their own when selecting autonomously the radio resources from radioresource pools (i.e., Mode2) or to provide this information to theeNodeB which in turn can then determine the radio resources basedthereon (Mode 1).

Correspondingly, the vehicular UEs will start by determining theirgeographical location so as to then identify the section and/orsubsection which corresponds to that geographical location. Therefore,the vehicular UEs need to know about how the road is exactly dividedinto sections and subsections, e.g., they need to know about the size ofthe section and the number and size of the various subsections intowhich each section is divided. Furthermore, the vehicle UEs may alsoneed to know where exactly the grid (i.e., sections/subsections) startsfor a particular road that they are traveling on. This information forinstance can be provided in the form of boundaries given by particulargeographical coordinates identifying the start and/or the end of roads.Therefore, a road shall be unambiguously divided into sections andsubsections, such that all the vehicular UEs and also the eNodeB havethe same understanding of where the sections and subsections are locatedand start and end.

Also, the vehicular UE shall adapt the grid and the correspondingsections and subsections such that they still align with the road evenwhen the road has curves.

It should be further noted, that the vehicular UE may be connected tothe navigation system of the vehicle and may thus have access to mapdata which assists the vehicular UE in determining the boundaries of theroad and how the road is divided into sections and/or subsections.

According to a further exemplary implementation, based on the mapinformation that is available from the navigational system of thevehicle, the vehicular UE should at least have access/ knowledge of aroad start/ end, the co-ordinates of the edges of the road, number oflanes in each direction, etc. On top of this it could apply thefollowing functions to calculate its section/ subsection. For thefollowing, the UE could use either the Decimal Degrees (DD) or the DMSvalues (https://en.wikipedia.org/wiki/Decimal_degrees)

A ,unit’ each for the length and width of the section/ subsection can besignaled in the Broadcast message, e.g., 0° 00′0.036″ representing1.1132 m. The network can signal that x′ unit of latitude/ ,y′ unit oflongitude constitute one section/ subsection, additionally based on theboundary Information of the road.

The above described implementations of the first embodiment implicitlyassumed that the vehicular UE is in coverage of the eNodeB. However, avehicular UE can also be out of coverage of the eNodeB and shall stillbe able to perform vehicular communication. Correspondingly, a furtherimplementation of the first embodiment takes this into account byspecifying at a vehicular UE which is out of coverage shall use theusual D2D resource allocation method without additionally consideringits vehicle location when determining the radio resources. For instance,the random radio resource selection should be reliable enough,especially taking into account that in areas where a particularvehicular UE is out of coverage should not have a lot of vehicles in thefirst place thus reducing the likelihood of a collision and thus causingthe benefits from additionally considering the vehicle location to beminimal.

Second Embodiment

In the following a second embodiment is presented which deals with thesame problem as the one solved by the first embodiment, i.e., the oneexplained at the beginning of the detailed description namely to improvethe radio resource allocation for vehicular communication. The secondembodiment is in many aspects similar to the first embodiment andreferences to the first embodiment will be often used.

As was explained above for the first embodiment, a central feature wasthat the first embodiment provided an additional, improved, resourceallocation method capable of additionally taking the location of thevehicular UE into account. Furthermore, as a further, optional,improvement to this location-assisted resource allocation, the firstembodiment allowed the vehicular UE to perform sensing on the allocatedradio resources before actually using them so as to avoid collisions onradio resources that are or will be in use by another UE.

According to the second embodiment, the central feature of theadditional, improved, resource allocation method is the additionalsensing capability of the vehicular UE(s), while the feature ofassisting the resource allocation by the vehicular UE location remainsoptional.

In more detail, the radio resource allocation according to the secondembodiment is also based on the radio resource allocation as alreadydefined for D2D communication, thus allowing Mode 1 and Mode 2 resourceallocations as explained in the background section. Similar to the firstembodiment, the second embodiment additionally distinguishes between twodifferent resource allocations, differing in that the vehicular UEadditionally performs sensing on the determined radio resources beforeactually using them.

As explained in detail for the first embodiment, the term sensingcapability shall be broadly understood as the capability of a vehicularUE to determine whether candidate radio resources are or will be used byother UEs or not. Then, these blocked radio resources shall, ifpossible, not be used so as to avoid corresponding collisions with theseother UEs. This sensing capability can be applied by the vehicular UEsfor both Mode 1 and Mode 2 resource allocations.

In particular, it is exemplarily assumed that the vehicular UE isconfigured for Mode-2 resource allocation, where the UE autonomouslyselects radio resources from a suitable radio resource pool. Inaddition, the vehicular UE shall perform sensing so as to not use radioresources that are or will be used by another UE. As explained in thefirst embodiment, the vehicular UE may first select a candidate set ofradio resources from a suitable radio resource pool and then determinewhether these selected candidate set of radio resources is actually usedby another mobile terminal or not. In case the radio resources areblocked, the vehicular UE shall select other resources from the radioresource pool and shall again perform the sensing procedure to make surethat these radio resources are free to use. On the other hand, thevehicular UE, before actually selecting a candidate set of radioresources from the radio resource pool, may perform the sensing on allradio resources of the radio resource pool so as to eliminate/disregardthose radio resources that are or will be in use by another mobileterminal. As a result, the vehicular UE will then select radio resourcesfrom among the remaining free radio resources of the radio resourcepool.

A further improvement to the sensing procedure is presented in thefollowing for the situation where all radio resources of a radioresource pool are or will be in use by another mobile terminal. In asimilar manner as already explained for the first embodiment, thevehicular UE shall be able to select radio resources from another radioresource pool in case no free radio resources are available. This otherradio resource pool may be still among the many resource pool configuredby the network for use of V2X communication. In case if there is onlyone resource pool configured, or, if the last configured resource poolalso turns out to be completely blocked, then this vehicular UE mustsimply wait and try again after some specified time duration.

On the other hand, the second embodiment is also applicable to the Mode1 resource allocation, where the vehicular UE has to request radioresources from the eNodeB by transmitting a scheduling request andpossibly a buffer status report to the eNodeB. In response, the eNodeBwill determine suitable radio resources and will provide the vehicularUE with a corresponding indication of the radio resources that are to beused. According to the second embodiment, the vehicular UE willdetermine whether the radio resources allocated by the eNodeB are orwill be used by another (vehicular) UE, and will not use them in casethere are blocked so as to avoid the collision. Rather, the vehicular UEmay then again request further radio resources from the eNodeB, or mayproceed to autonomously select radio resources from a suitable radioresource pool (i.e., Mode 2) so as to avoid the delay incurred by havingto again request radio resources from the eNodeB.

As explained in detail for the first embodiment, there are at least twopossible ways that the vehicular UE can determine whether radioresources will be blocked by another UE, and thus reference is made tothe corresponding passages of the first embodiment. In brief, thevehicular UE may measure that received signal strength and compare sameto a threshold, so as to then determine that radio resources are alreadyin use in case the received signal strength is larger than thethreshold. Alternatively, or in addition, the vehicular UE may monitorscheduling assignment messages transmitted by other vehicular UEs so asto collect information on which radio resources will be used by otherUEs and thus will be blocked from being used by the vehicular UE.

Additionally including the sensing procedure for the radio resourceallocation is especially advantageous in scenarios where radio resourcecollisions are likely to happen. This may be the case when a radioresource pool is relatively small but used by many vehicular UEs, e.g.,in situations where many vehicular UEs are located side-by-side, such asin a traffic jam.

After having explained the sensing capability of the vehicular UE indetail, the second embodiment shall make use of the sensing capabilityin a selective way. In a similar manner as in the first embodiment, anentity of the mobile communication system, such as the eNodeB, the MME,or a ProSe-related entity in the core network, can take a decision onwhether to use a normal D2D resource allocation method or whether to usethe improved sensing-assisted resource allocation method introduced withthe second embodiment. The responsible entity, for ease of explanationassumed to be the eNodeB, can take the decision based on differentinformation. For instance, the eNodeB can take the topology of theparticular area of its cell into account (e.g., highway or city centeror rural, etc.), as well as the number and speed of vehicles in theparticular area. Furthermore, whether to use the sensing-assistedresource allocation or without sensing-assistance may also depend on thetime, for instance peak hours where the traffic is usually dense whileat other times the traffic situation is different.

Consequently, the eNodeB will selectively decide whether to use one orthe other resource allocation method, i.e., whether to use or not usethe additional capability of sensing so as to avoid collisions. Inaccordance therewith, the vehicular UE is to be provided withinformation from which it may deduce which resource allocation method touse. As already explained for the first embodiment, this may be done invarious ways, also depending on whether the eNodeB takes the samedecision for all vehicular UEs in its cell or not. An explicitinformation (e.g., flag) can be used in said respect, being broadcast inits radio cell or being transmitted in dedicated messages to particularvehicular UEs. Alternatively, or in addition, instead of providing anexplicit instruction to the vehicular UE, it may also be possible forthe vehicular UE to derive from internal parameters which resourceallocation method to use. In particular, in order to perform the sensingit may be necessary that the UE is provided with particular parameterssuch as the thresholds for the comparison of the received signalstrength or the periodicity with which the UE shall monitor for SAmessages.

Optionally, the SA message itself might contain information about theperiod of intended use of the resources, e.g., in next few TTIs orcontrol/ data cycles, etc., called here as the “Busy-ness” period. Inthis respect, individual candidate SA messages (PSCCH) would be receivedand decoded and the vehicular mobile terminal can check if theseindicate any future “busy-ness” in coming control/ Data cycles. If anindividual candidate SA is not being transmitted currently, thevehicular UE could assume the control (SA) and the corresponding Dataresources as “free”. The “busy-ness” in SA message may also indicate acorresponding period of busy-ness during which it intends to keeptransmitting on the corresponding control/ Data resources. In thesimplest form it will be a Boolean value indicating “busy-ness” periodas 1 cycle or some other ‘fixed’ number of Cycles.

In any case, according to the various implementations of the secondembodiment, each of the vehicular UEs shall know at any time whether touse one or the other of the two resource allocation methods, i.e.,whether to apply sensing or not in addition.

Furthermore, the second embodiment may be also enhanced, on top of thesensing capability, by assisting the radio resource allocation with thelocation of the vehicular UE. As was explained in detail for the firstembodiment, the vehicular UEs may determine its location and use saidlocation in the process of determining the radio resources forcommunication with the other mobile terminals. Correspondingly,particular implementations of the second embodiment combine the sensingcapability as well as the location-assisted resource allocation asexplained for the first embodiment. In order to avoid repetition,reference is made to the particular passages of the first embodimentdealing in detail with the various different implementations of thefirst embodiment regarding how the vehicular UE location can bedetermined by the UEs (either as simple geographical coordinates or as afunction of subsections of a road), how the vehicular UE location can beused when determining the radio resources either in Mode 1 or Mode 2,how the vehicular UE location can be expressed as geographicalcoordinates or as a function of sections and/or subsections of a road,how a road can be divided into sections/subsections, how the vehicularUE location can be transmitted to the eNodeB for the Mode 1 resourceallocation, etc.

Hardware and Software Implementation of the Present Disclosure

Other exemplary embodiments relate to the implementation of the abovedescribed various embodiments using hardware, software, or software incooperation with hardware. In this connection a user terminal (mobileterminal) is provided. The user terminal is adapted to perform themethods described herein, including corresponding entities toparticipate appropriately in the methods, such as receiver, transmitter,processors.

It is further recognized that the various embodiments may be implementedor performed using computing devices (processors). A computing device orprocessor may for example be general purpose processors, digital signalprocessors (DSP), application specific integrated circuits (ASIC), fieldprogrammable gate arrays (FPGA) or other programmable logic devices,etc. The various embodiments may also be performed or embodied by acombination of these devices. In particular, each functional block usedin the description of each embodiment described above can be realized byan LSI as an integrated circuit. They may be individually formed aschips, or one chip may be formed so as to include a part or all of thefunctional blocks. They may include a data input and output coupledthereto. The LSI here may be referred to as an IC, a system LSI, a superLSI, or an ultra LSI depending on a difference in the degree ofintegration. However, the technique of implementing an integratedcircuit is not limited to the LSI and may be realized by using adedicated circuit or a general-purpose processor. In addition, a FPGA(Field Programmable Gate Array) that can be programmed after themanufacture of the LSI or a reconfigurable processor in which theconnections and the settings of circuits cells disposed inside the LSIcan be reconfigured may be used.

Further, the various embodiments may also be implemented by means ofsoftware modules, which are executed by a processor or directly inhardware. Also a combination of software modules and a hardwareimplementation may be possible. The software modules may be stored onany kind of computer readable storage media, for example RAM, EPROM,EEPROM, flash memory, registers, hard disks, CD-ROM, DVD, etc. It shouldbe further noted that the individual features of the differentembodiments may individually or in arbitrary combination be subjectmatter to another embodiment.

It would be appreciated by a person skilled in the art that numerousvariations and/or modifications may be made to the present disclosure asshown in the specific embodiments. The present embodiments are,therefore, to be considered in all respects to be illustrative and notrestrictive.

The various embodiments described above can be combined to providefurther embodiments. All of the U.S. patents, U.S. patent applicationpublications, U.S. patent applications, foreign patents, foreign patentapplications and non-patent publications referred to in thisspecification and/or listed in the Application Data Sheet areincorporated herein by reference, in their entirety. Aspects of theembodiments can be modified, if necessary to employ concepts of thevarious patents, applications and publications to provide yet furtherembodiments.

These and other changes can be made to the embodiments in light of theabove-detailed description. In general, in the following claims, theterms used should not be construed to limit the claims to the specificembodiments disclosed in the specification and the claims, but should beconstrued to include all possible embodiments along with the full scopeof equivalents to which such claims are entitled. Accordingly, theclaims are not limited by the disclosure.

1. A radio base station, comprising: control circuitry, which, inoperation, generates parameter information; and transmission circuitry,which, in operation, transmits to a user equipment the parameterinformation in a cell in which the user equipment is located, whereinthe parameter information, when indicating use of radio resources whichcorrespond to a geographical location of the user equipment, defines alocation subsection in which the user equipment is geographicallylocated, wherein the parameter information includes a first parameterindicative of a length of the location subsection, a second parameterindicative of a width of the location subsection, a third parameterindicative of a number of location subsections with respect to thelength in longitude into which a location section is divided, and afourth parameter indicative of a number of location subsections withrespect to the width in latitude into which the location section isdivided, wherein, the transmission circuitry, in operation, dynamicallysignals the first to fourth parameters to the user equipment, and theuser equipment, based on the first to four parameters, dynamicallydetermines radio resources which correspond to the location subsectionin which the user equipment is geographically located.
 2. The radio basestation according to claim 1, wherein the radio resources whichcorrespond to the location subsection are radio resources in a radioresource pool associated with the location subsection.
 3. The radio basestation according to claim 1, wherein the transmission circuitry, inoperation, transmits to the user equipment a configuration of radioresource pools associated with different geographical locations, whereinthe configuration of radio resource pools is defined by explicitinformation on the radio resource pools and radio resources in eachradio resource pool, or by rules defining how radio resources aredivided into the radio resource pools.
 4. The radio base stationaccording to claim 1, comprising: reception circuitry, which, inoperation, receives, from the user equipment, location information onthe geographical location of the user equipment, wherein the locationinformation includes geographical coordinates or an identifier of alocation section in which the user equipment is geographically located.5. The radio base station according to claim 1, wherein the parameterinformation indicates potential radio resources possibly used by anotheruser equipment.
 6. The radio base station according to claim 5, whereinthe parameter information indicates a potential radio resource pool,which includes the potential radio resources and which is possibly usedby the another user equipment.
 7. The radio base station according toclaim 1, wherein the geographical location of the user equipment isdefined by a grid overlaying a road on which the user equipment islocated, the road is divided into a plurality of location sections, andeach of the plurality of location sections covers all lanes in the road,wherein all of the plurality of location sections are subdivided into asame number of non-overlapping location subsections, and each of thelocation subsections covers at least one of the lanes in the road, andwherein each of the location subsections is associated with a radioresource pool.
 8. The radio base station according to claim 7, whereinthe radio resources associated with the location subsections areorthogonal to each other to mitigate interference.
 9. The radio basestation according to claim 1, wherein the location subsection isassociated with a subsection identifier and the location section isassociated with a section identifier.
 10. The radio base stationaccording to claim 1, wherein the parameter information indicates use ofradio resources which correspond to the geographic location of the userequipment when the user equipment is in coverage of the radio basestation.
 11. A method performed by a radio base station, the methodcomprising: generating parameter information; transmitting to a userequipment the parameter information in a cell in which the userequipment is located, wherein the parameter information, when indicatinguse of radio resources which correspond to a geographical location ofthe user equipment, defines a location subsection in which the userequipment is geographically located, wherein the parameter informationincludes a first parameter indicative of a length of the locationsubsection, a second parameter indicative of a width of the locationsubsection, a third parameter indicative of a number of locationsubsections with respect to the length in longitude into which alocation section is divided, and a fourth parameter indicative of anumber of location subsections with respect to the width in latitudeinto which the location section is divided; and dynamically signalingthe first to fourth parameters to the user equipment, wherein the userequipment, based on the first to four parameters, dynamically determinesradio resources which correspond to the location subsection in which theuser equipment is geographically located.